Repo created

app/autodiscovery/api/build.gradle.kts

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+@Suppress("DSL_SCOPE_VIOLATION")
+plugins {
+    id(ThunderbirdPlugins.Library.jvm)
+    alias(libs.plugins.android.lint)
+}
+
+dependencies {
+    api(projects.mail.common)
+}

app/autodiscovery/api/src/main/java/com/fsck/k9/autodiscovery/api/ConnectionSettingsDiscovery.kt

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+package com.fsck.k9.autodiscovery.api
+
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+
+interface ConnectionSettingsDiscovery {
+    fun discover(email: String): DiscoveryResults?
+}
+
+data class DiscoveryResults(val incoming: List<DiscoveredServerSettings>, val outgoing: List<DiscoveredServerSettings>)
+
+data class DiscoveredServerSettings(
+    val protocol: String,
+    val host: String,
+    val port: Int,
+    val security: ConnectionSecurity,
+    val authType: AuthType?,
+    val username: String?
+)

app/autodiscovery/providersxml/build.gradle.kts

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+plugins {
+    id(ThunderbirdPlugins.Library.android)
+}
+
+dependencies {
+    implementation(projects.app.core)
+    implementation(projects.mail.common)
+    implementation(projects.app.autodiscovery.api)
+
+    implementation(libs.timber)
+
+    testImplementation(projects.app.testing)
+    testImplementation(projects.backend.imap)
+    testImplementation(libs.robolectric)
+    testImplementation(libs.androidx.test.core)
+}
+
+android {
+    namespace = "com.fsck.k9.autodiscovery.providersxml"
+}

app/autodiscovery/providersxml/src/main/java/com/fsck/k9/autodiscovery/providersxml/KoinModule.kt

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+package com.fsck.k9.autodiscovery.providersxml
+
+import org.koin.dsl.module
+
+val autodiscoveryProvidersXmlModule = module {
+    factory { ProvidersXmlProvider(context = get()) }
+    factory { ProvidersXmlDiscovery(xmlProvider = get(), oAuthConfigurationProvider = get()) }
+}

app/autodiscovery/providersxml/src/main/java/com/fsck/k9/autodiscovery/providersxml/ProvidersXmlDiscovery.kt

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+package com.fsck.k9.autodiscovery.providersxml
+
+import android.content.res.XmlResourceParser
+import android.net.Uri
+import com.fsck.k9.autodiscovery.api.ConnectionSettingsDiscovery
+import com.fsck.k9.autodiscovery.api.DiscoveredServerSettings
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+import com.fsck.k9.helper.EmailHelper
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+import com.fsck.k9.oauth.OAuthConfigurationProvider
+import com.fsck.k9.preferences.Protocols
+import org.xmlpull.v1.XmlPullParser
+import timber.log.Timber
+
+class ProvidersXmlDiscovery(
+    private val xmlProvider: ProvidersXmlProvider,
+    private val oAuthConfigurationProvider: OAuthConfigurationProvider
+) : ConnectionSettingsDiscovery {
+
+    override fun discover(email: String): DiscoveryResults? {
+        val domain = EmailHelper.getDomainFromEmailAddress(email) ?: return null
+
+        val provider = findProviderForDomain(domain) ?: return null
+
+        val incomingSettings = provider.toIncomingServerSettings(email) ?: return null
+        val outgoingSettings = provider.toOutgoingServerSettings(email) ?: return null
+        return DiscoveryResults(listOf(incomingSettings), listOf(outgoingSettings))
+    }
+
+    private fun findProviderForDomain(domain: String): Provider? {
+        return try {
+            xmlProvider.getXml().use { xml ->
+                parseProviders(xml, domain)
+            }
+        } catch (e: Exception) {
+            Timber.e(e, "Error while trying to load provider settings.")
+            null
+        }
+    }
+
+    private fun parseProviders(xml: XmlResourceParser, domain: String): Provider? {
+        do {
+            val xmlEventType = xml.next()
+            if (xmlEventType == XmlPullParser.START_TAG && xml.name == "provider") {
+                val providerDomain = xml.getAttributeValue(null, "domain")
+                if (domain.equals(providerDomain, ignoreCase = true)) {
+                    val provider = parseProvider(xml)
+                    if (provider != null) return provider
+                }
+            }
+        } while (xmlEventType != XmlPullParser.END_DOCUMENT)
+
+        return null
+    }
+
+    private fun parseProvider(xml: XmlResourceParser): Provider? {
+        var incomingUriTemplate: String? = null
+        var incomingUsernameTemplate: String? = null
+        var outgoingUriTemplate: String? = null
+        var outgoingUsernameTemplate: String? = null
+
+        do {
+            val xmlEventType = xml.next()
+            if (xmlEventType == XmlPullParser.START_TAG) {
+                when (xml.name) {
+                    "incoming" -> {
+                        incomingUriTemplate = xml.getAttributeValue(null, "uri")
+                        incomingUsernameTemplate = xml.getAttributeValue(null, "username")
+                    }
+                    "outgoing" -> {
+                        outgoingUriTemplate = xml.getAttributeValue(null, "uri")
+                        outgoingUsernameTemplate = xml.getAttributeValue(null, "username")
+                    }
+                }
+            }
+        } while (!(xmlEventType == XmlPullParser.END_TAG && xml.name == "provider"))
+
+        return if (incomingUriTemplate != null && incomingUsernameTemplate != null && outgoingUriTemplate != null &&
+            outgoingUsernameTemplate != null
+        ) {
+            Provider(incomingUriTemplate, incomingUsernameTemplate, outgoingUriTemplate, outgoingUsernameTemplate)
+        } else {
+            null
+        }
+    }
+
+    private fun Provider.toIncomingServerSettings(email: String): DiscoveredServerSettings? {
+        val user = EmailHelper.getLocalPartFromEmailAddress(email) ?: return null
+        val domain = EmailHelper.getDomainFromEmailAddress(email) ?: return null
+
+        val username = incomingUsernameTemplate.fillInUsernameTemplate(email, user, domain)
+
+        val security = when {
+            incomingUriTemplate.startsWith("imap+ssl") -> ConnectionSecurity.SSL_TLS_REQUIRED
+            incomingUriTemplate.startsWith("imap+tls") -> ConnectionSecurity.STARTTLS_REQUIRED
+            else -> error("Connection security required")
+        }
+
+        val uri = Uri.parse(incomingUriTemplate)
+        val host = uri.host ?: error("Host name required")
+        val port = if (uri.port == -1) {
+            if (security == ConnectionSecurity.STARTTLS_REQUIRED) 143 else 993
+        } else {
+            uri.port
+        }
+
+        val authType = if (oAuthConfigurationProvider.getConfiguration(host) != null) {
+            AuthType.XOAUTH2
+        } else {
+            AuthType.PLAIN
+        }
+
+        return DiscoveredServerSettings(Protocols.IMAP, host, port, security, authType, username)
+    }
+
+    private fun Provider.toOutgoingServerSettings(email: String): DiscoveredServerSettings? {
+        val user = EmailHelper.getLocalPartFromEmailAddress(email) ?: return null
+        val domain = EmailHelper.getDomainFromEmailAddress(email) ?: return null
+
+        val username = outgoingUsernameTemplate.fillInUsernameTemplate(email, user, domain)
+
+        val security = when {
+            outgoingUriTemplate.startsWith("smtp+ssl") -> ConnectionSecurity.SSL_TLS_REQUIRED
+            outgoingUriTemplate.startsWith("smtp+tls") -> ConnectionSecurity.STARTTLS_REQUIRED
+            else -> error("Connection security required")
+        }
+
+        val uri = Uri.parse(outgoingUriTemplate)
+        val host = uri.host ?: error("Host name required")
+        val port = if (uri.port == -1) {
+            if (security == ConnectionSecurity.STARTTLS_REQUIRED) 587 else 465
+        } else {
+            uri.port
+        }
+
+        val authType = if (oAuthConfigurationProvider.getConfiguration(host) != null) {
+            AuthType.XOAUTH2
+        } else {
+            AuthType.PLAIN
+        }
+
+        return DiscoveredServerSettings(Protocols.SMTP, host, port, security, authType, username)
+    }
+
+    private fun String.fillInUsernameTemplate(email: String, user: String, domain: String): String {
+        return this.replace("\$email", email).replace("\$user", user).replace("\$domain", domain)
+    }
+
+    internal data class Provider(
+        val incomingUriTemplate: String,
+        val incomingUsernameTemplate: String,
+        val outgoingUriTemplate: String,
+        val outgoingUsernameTemplate: String
+    )
+}

app/autodiscovery/providersxml/src/main/java/com/fsck/k9/autodiscovery/providersxml/ProvidersXmlProvider.kt

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+package com.fsck.k9.autodiscovery.providersxml
+
+import android.content.Context
+import android.content.res.XmlResourceParser
+
+class ProvidersXmlProvider(private val context: Context) {
+    fun getXml(): XmlResourceParser {
+        return context.resources.getXml(R.xml.providers)
+    }
+}

app/autodiscovery/providersxml/src/main/res/xml/providers.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2008 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+  
+          http://www.apache.org/licenses/LICENSE-2.0
+  
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+    <!--
+        This file is used to specify providers that we know default settings for
+        so that the user can set up their account by simply entering their email
+        address and password.
+
+        When a user starts this process, the email address is parsed, the domain
+        broken out and used to search this file for a provider. If one is found the
+        provider's settings are used to attempt to connect to the account.
+        
+        At this time, the id and label attributes are not used.  However, please include them
+        if you make edits to this file.  id must also be completely unique.  label will be shown
+        to the user when there are multiple options provided for a single domain (not currently
+        supported).
+
+        A provider contains the settings for setting up an email account
+        that ends with the given domain. Domains should be unique within
+        this file. Each provider should have at least one incoming section and
+        one outgoing section. If more than one is specified only the first
+        will be used.
+
+        Valid incoming uri schemes are:
+            imap+tls+   IMAP with required TLS transport security.
+                            If TLS is not available the connection fails.
+            imap+ssl+   IMAP with required SSL transport security.
+                            If SSL is not available the connection fails.
+
+        Valid outgoing uri schemes are:
+            smtp+tls+   SMTP with required TLS transport security.
+                            If TLS is not available the connection fails.
+            smtp+ssl+   SMTP with required SSL transport security.
+                            If SSL is not available the connection fails.
+
+        The URIs should be full templates for connection, including a port if
+        the service uses a non-default port.  The default ports are as follows:
+            imap+tls+   143     smtp+tls+   587
+            imap+ssl+   993     smtp+ssl+   465
+
+        The username attribute is used to supply a template for the username
+        that will be presented to the server. This username is built from a
+        set of variables that are substituted with parts of the user
+        specified email address.
+
+        Valid substitution values for the username attribute are:
+            $email - the email address the user entered
+            $user - the value before the @ sign in the email address the user entered
+            $domain - the value after the @ sign in the email address the user entered
+            
+        The username attribute MUST be specified for the incoming element, so the IMAP
+        server can identify the mailbox to be opened.
+        
+        The username attribute MAY be the empty string for the outgoing element, but only if the 
+        SMTP server supports anonymous transmission (most don't).
+
+        While it would technically work please DO NOT add providers that don't support encrypted
+        connections.
+    -->
+
+<providers>
+
+    <!-- Gmail variants -->
+    <provider id="gmail" label="Gmail" domain="gmail.com">
+        <incoming uri="imap+ssl+://imap.gmail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.gmail.com" username="$email" />
+    </provider>
+    <provider id="googlemail" label="Google Mail" domain="googlemail.com">
+        <incoming uri="imap+ssl+://imap.googlemail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.googlemail.com" username="$email" />
+    </provider>
+    <provider id="google" label="Google" domain="google.com">
+        <incoming uri="imap+ssl+://imap.gmail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.gmail.com" username="$email" />
+    </provider>
+    <provider id="android" label="Android" domain="android.com">
+        <incoming uri="imap+ssl+://imap.gmail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.gmail.com" username="$email" />
+    </provider>
+
+    <!-- USA -->
+    <provider id="comcast" label="Comcast" domain="comcast.net">
+        <incoming uri="imap+ssl+://imap.comcast.net" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.comcast.net" username="$email" />
+    </provider>
+    <provider id="montclair.edu" label="MSU" domain="montclair.edu">
+        <incoming uri="imap+ssl+://mail.montclair.edu" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.montclair.edu" username="$user" />
+    </provider>
+    <provider id="gmx.com" label="GMX" domain="gmx.com">
+        <incoming uri="imap+ssl+://imap.gmx.com" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.gmx.com" username="$email" />
+    </provider>
+    <provider id="zoho.com" label="Zoho Mail" domain="zoho.com">
+    	<incoming uri="imap+ssl+://imap.zoho.com" username="$email" />
+    	<outgoing uri="smtp+tls+://smtp.zoho.com" username="$email" />
+    </provider>
+    <provider id="riseup" label="Riseup Networks" domain="riseup.net">
+    	<incoming uri="imap+ssl+://mail.riseup.net" username="$user" />
+    	<outgoing uri="smtp+tls+://mail.riseup.net" username="$user" />
+    </provider>	
+
+    <!-- Mail.com Variants -->
+    <provider id="mail.com" label="Mail.com" domain="mail.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="email.com" label="Mail.com" domain="email.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="techie.com" label="Mail.com" domain="techie.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="email.com" label="Mail.com" domain="email.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="usa.com" label="Mail.com" domain="usa.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="myself.com" label="Mail.com" domain="myself.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="consultant.com" label="Mail.com" domain="consultant.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="post.com" label="Mail.com" domain="post.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="europe.com" label="Mail.com" domain="europe.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="asia.com" label="Mail.com" domain="asia.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="iname.com" label="Mail.com" domain="iname.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="writeme.com" label="Mail.com" domain="writeme.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="dr.com" label="Mail.com" domain="dr.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="engineer.com" label="Mail.com" domain="engineer.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="cheerful.com" label="Mail.com" domain="cheerful.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="accountant.com" label="Mail.com" domain="accountant.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="techie.com" label="Mail.com" domain="techie.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="linuxmail.org" label="Mail.com" domain="linuxmail.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="uymail.com" label="Mail.com" domain="uymail.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+    <provider id="contractor.net" label="Mail.com" domain="contractor.com">
+        <incoming uri="imap+ssl+://imap.mail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.com" username="$email" />
+    </provider>
+
+    <!-- Yahoo! Mail Variants -->
+    <provider id="yahoo" label="Yahoo" domain="yahoo.com">
+        <incoming uri="imap+ssl+://imap.mail.yahoo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.yahoo.com" username="$email" />
+    </provider>
+    <provider id="yahoo.de" label="Yahoo" domain="yahoo.de">
+        <incoming uri="imap+ssl+://imap.mail.yahoo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.yahoo.com" username="$email" />
+    </provider>
+    <provider id="ymail" label="YMail" domain="ymail.com">
+        <incoming uri="imap+ssl+://imap.mail.yahoo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.yahoo.com" username="$email" />
+    </provider>
+    <provider id="rocketmail" label="Rocketmail" domain="rocketmail.com">
+        <incoming uri="imap+ssl+://imap.mail.yahoo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.yahoo.com" username="$email" />
+    </provider>
+    
+    <!-- Apple -->
+    <provider id="apple" label="Apple" domain="apple.com">
+        <incoming uri="imap+ssl+://imap.mail.apple.com" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.mail.apple.com" username="$user" />
+    </provider>
+    <provider id="dotmac" label=".Mac" domain="mac.com">
+        <incoming uri="imap+ssl+://imap.mail.mac.com" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.mail.mac.com" username="$user" />
+    </provider>
+    <provider id="mobileme" label="MobileMe" domain="me.com">
+        <incoming uri="imap+ssl+://imap.mail.me.com" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.mail.me.com" username="$user" />
+    </provider>
+    <provider id="icloud" label="iCloud" domain="icloud.com">
+        <incoming uri="imap+ssl+://imap.mail.icloud.com" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.mail.icloud.com" username="$user" />
+    </provider>
+
+    <!-- Australia -->
+    <provider id="fastmail-fm" label="Fastmail" domain="fastmail.fm">
+        <incoming uri="imap+ssl+://mail.messagingengine.com" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.messagingengine.com" username="$email" />
+    </provider>
+
+    <!-- Virgin Media variants -->
+    <provider id="virginmedia.com" label="Virgin Media" domain="virginmedia.com">
+        <incoming uri="imap+ssl+://imap.virginmedia.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.virginmedia.com" username="$email" />
+    </provider>
+    <provider id="virgin.net" label="Virgin Media" domain="virgin.net">
+        <incoming uri="imap+ssl+://imap.virginmedia.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.virginmedia.com" username="$email" />
+    </provider>
+    <provider id="blueyonder.co.uk" label="Virgin Media" domain="blueyonder.co.uk">
+        <incoming uri="imap+ssl+://imap.virginmedia.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.virginmedia.com" username="$email" />
+    </provider>
+    <provider id="ntlworld.com" label="Virgin Media" domain="ntlworld.com">
+        <incoming uri="imap+ssl+://imap.virginmedia.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.virginmedia.com" username="$email" />
+    </provider>
+    
+    <!-- France -->
+    <provider id="mailo.com" label="mailo.com" domain="mailo.com">
+        <incoming uri="imap+ssl+://mail.mailo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.mailo.com" username="$email" />
+    </provider>
+    <provider id="net-c.fr" label="net-c.fr" domain="net-c.fr">
+        <incoming uri="imap+ssl+://mail.mailo.com" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.mailo.com" username="$email" />
+    </provider>
+
+    <!-- Germany -->
+    <provider id="mailbox.org" label="mailbox.org" domain="mailbox.org">
+        <incoming uri="imap+tls+://imap.mailbox.org" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.mailbox.org" username="$email" />
+    </provider>
+    <provider id="freenet" label="Freenet" domain="freenet.de">
+        <incoming uri="imap+tls+://mx.freenet.de" username="$email" />
+        <outgoing uri="smtp+tls+://mx.freenet.de" username="$email" />
+    </provider>
+    <provider id="T-Online" label="T-Online" domain="t-online.de">
+        <incoming uri="imap+ssl+://secureimap.t-online.de" username="$email" />
+        <outgoing uri="smtp+tls+://securesmtp.t-online.de" username="$email" />
+    </provider>
+    <provider id="web.de" label="Web.de" domain="web.de">
+        <incoming uri="imap+ssl+://imap.web.de" username="$user" />
+        <outgoing uri="smtp+tls+://smtp.web.de" username="$user" />
+    </provider>
+    <provider id="posteo" label="Posteo" domain="posteo.net">
+        <incoming uri="imap+tls+://posteo.de" username="$email" />
+        <outgoing uri="smtp+tls+://posteo.de" username="$email" />
+    </provider>    
+    <provider id="posteo" label="Posteo" domain="posteo.de">
+        <incoming uri="imap+tls+://posteo.de" username="$email" />
+        <outgoing uri="smtp+tls+://posteo.de" username="$email" />
+    </provider>
+    <provider id="systemliorg" label="systemli.org" domain="systemli.org">
+        <incoming uri="imap+ssl+://mail.systemli.org" username="$email" />
+        <outgoing uri="smtp+tls+://mail.systemli.org" username="$email" />
+    </provider>
+
+    <!-- GMX variants -->
+    <provider id="gmx.net" label="GMX.net" domain="gmx.net">
+        <incoming uri="imap+ssl+://imap.gmx.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.gmx.net" username="$email" />
+    </provider>
+    <provider id="gmx.de" label="GMX.de" domain="gmx.de">
+        <incoming uri="imap+ssl+://imap.gmx.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.gmx.net" username="$email" />
+    </provider>
+    <provider id="gmx.at" label="GMX.at" domain="gmx.at">
+        <incoming uri="imap+ssl+://imap.gmx.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.gmx.net" username="$email" />
+    </provider>
+    <provider id="gmx.ch" label="GMX.ch" domain="gmx.ch">
+        <incoming uri="imap+ssl+://imap.gmx.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.gmx.net" username="$email" />
+    </provider>
+    <provider id="gmx.eu" label="GMX.eu" domain="gmx.eu">
+        <incoming uri="imap+ssl+://imap.gmx.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.gmx.net" username="$email" />
+    </provider>
+
+     <!-- Greece -->
+    <provider id="otenet.gr" label="otenet.gr" domain="otenet.gr">
+        <incoming uri="imap+ssl+://imap.otenet.gr" username="$email" />
+        <outgoing uri="smtp+tls+://mailgate.otenet.gr" username="$email" />
+    </provider>
+    <provider id="cosmotemail.gr" label="cosmotemail" domain="cosmotemail.gr">
+        <incoming uri="imap+ssl+://imap.cosmotemail.gr" username="$email" />
+        <outgoing uri="smtp+tls+://mailgate.cosmotemail.gr" username="$email" />
+    </provider>
+    <provider id="mycosmos.gr" label="mycosmos" domain="mycosmos.gr">
+        <incoming uri="imap+ssl+://mail.mycosmos.gr" username="$email" />
+        <outgoing uri="smtp+tls+://mail.mycosmos.gr" username="$email" />
+    </provider>
+    <provider id="espiv" label="Espiv.net" domain="espiv.net">
+        <incoming uri="imap+ssl+://mail.espiv.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.espiv.net" username="$email" />
+    </provider>
+    <provider id="squat" label="Squat.gr" domain="squat.gr">
+        <incoming uri="imap+ssl+://mail.espiv.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.espiv.net" username="$email" />
+    </provider>
+
+   <!-- Italy -->
+   <provider id="poste" label="poste" domain="poste.it">
+        <incoming uri="imap+ssl+://relay.poste.it" username="$email" />
+        <outgoing uri="smtp+ssl+://relay.poste.it" username="$email" />
+   </provider> 
+   <provider id="vodafone" label="vodafone" domain="vodafone.it">
+        <incoming uri="imap+ssl+://imap.vodafone.it" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.vodafone.it" username="$email" />
+   </provider> 
+
+   <!-- Switzerland -->
+    <!-- KolabNow.com variants -->
+    <provider id="kolabnow.com" label="KolabNow.com" domain="kolabnow.com">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="attorneymail.ch" label="KolabNow.com" domain="attorneymail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="barmail.ch" label="KolabNow.com" domain="barmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="collaborative.li" label="KolabNow.com" domain="collaborative.li">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="diplomail.ch" label="KolabNow.com" domain="diplomail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="groupoffice.ch" label="KolabNow.com" domain="groupoffice.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="journalistmail.ch" label="KolabNow.com" domain="journalistmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="legalprivilege.ch" label="KolabNow.com" domain="legalprivilege.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="libertymail.co" label="KolabNow.com" domain="libertymail.co">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="libertymail.net" label="KolabNow.com" domain="libertymail.net">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="mailatlaw.ch" label="KolabNow.com" domain="mailatlaw.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="medmail.ch" label="KolabNow.com" domain="medmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="mykolab.ch" label="KolabNow.com" domain="mykolab.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="mykolab.com" label="KolabNow.com" domain="mykolab.com">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="myswissmail.ch" label="KolabNow.com" domain="myswissmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="opengroupware.ch" label="KolabNow.com" domain="opengroupware.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="pressmail.ch" label="KolabNow.com" domain="pressmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="swisscollab.ch" label="KolabNow.com" domain="swisscollab.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="swissgroupware.ch" label="KolabNow.com" domain="swissgroupware.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="switzerlandmail.ch" label="KolabNow.com" domain="switzerlandmail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+    <provider id="trusted-legal-mail.ch" label="KolabNow.com" domain="trusted-legal-mail.ch">
+        <incoming uri="imap+ssl+://imap.kolabnow.com" username="$email" />
+        <outgoing uri="smtp+tls+://smtp.kolabnow.com" username="$email" />
+    </provider>
+
+   <!-- Japanese -->
+    <provider id="auone" label="au one" domain="auone.jp">
+        <incoming uri="imap+ssl+://imap.gmail.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.gmail.com" username="$email" />
+    </provider>
+
+   <!-- Korean -->
+    <provider id="naver" label="Naver" domain="naver.com">
+        <incoming uri="imap+ssl+://imap.naver.com"  username="$user" />
+        <outgoing uri="smtp+tls+://smtp.naver.com:587" username="$user" />
+    </provider>
+    <provider id="hanmail" label="Hanmail" domain="hanmail.net">
+        <incoming uri="imap+ssl+://imap.hanmail.net"  username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.hanmail.net" username="$user" />
+    </provider>
+    <provider id="daum" label="Hanmail" domain="daum.net">
+        <incoming uri="imap+ssl+://imap.hanmail.net"  username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.hanmail.net" username="$user" />
+    </provider>
+    
+   <!-- Russia -->
+    <!-- Mail.Ru variants -->
+    <provider id="rumailmailimap" label="mail.ru" domain="mail.ru">
+        <incoming uri="imap+ssl+://imap.mail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.ru" username="$email" />
+    </provider>
+    <provider id="rumailinboximap" label="inbox.ru" domain="inbox.ru">
+        <incoming uri="imap+ssl+://imap.mail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.ru" username="$email" />
+    </provider>
+    <provider id="rumaillistimap" label="list.ru" domain="list.ru">
+        <incoming uri="imap+ssl+://imap.mail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.ru" username="$email" />
+    </provider>
+    <provider id="rumailbkimap" label="bk.ru" domain="bk.ru">
+        <incoming uri="imap+ssl+://imap.mail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail.ru" username="$email" />
+    </provider>
+    <!-- Yandex variants -->
+    <provider id="comyanyandeximap" label="yandex.com" domain="yandex.com">
+        <incoming uri="imap+ssl+://imap.yandex.com" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.yandex.com" username="$user" />
+    </provider>
+    <provider id="ruyanyandeximap" label="yandex.ru" domain="yandex.ru">
+        <incoming uri="imap+ssl+://imap.yandex.ru" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.yandex.ru" username="$user" />
+    </provider>
+    <provider id="ruyanyaimap" label="ya.ru" domain="ya.ru">
+        <incoming uri="imap+ssl+://imap.ya.ru" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.ya.ru" username="$user" />
+    </provider>
+    <provider id="byyandeximap" label="yandex.by" domain="yandex.by">
+        <incoming uri="imap+ssl+://imap.yandex.by" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.yandex.by" username="$user" />
+    </provider>
+    <provider id="kzyandeximap" label="yandex.kz" domain="yandex.kz">
+        <incoming uri="imap+ssl+://imap.yandex.kz" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.yandex.kz" username="$user" />
+    </provider>
+    <provider id="uayandeximap" label="yandex.ua" domain="yandex.ua">
+        <incoming uri="imap+ssl+://imap.yandex.ua" username="$user" />
+        <outgoing uri="smtp+ssl+://smtp.yandex.ua" username="$user" />
+    </provider>
+    <!-- Rambler.ru variants -->
+    <provider id="ruramramblerimap" label="rambler.ru" domain="rambler.ru">
+        <incoming uri="imap+ssl+://mail.rambler.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.rambler.ru" username="$email" />
+    </provider>
+    <provider id="ruramlentaimap" label="lenta.ru" domain="lenta.ru">
+        <incoming uri="imap+ssl+://mail.rambler.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.rambler.ru" username="$email" />
+    </provider>
+    <provider id="ruramroimap" label="ro.ru" domain="ro.ru">
+        <incoming uri="imap+ssl+://mail.rambler.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://mail.rambler.ru" username="$email" />
+    </provider>
+    <!-- QIP.RU variants -->
+    <provider id="ruqipqipimap" label="qip.ru" domain="qip.ru">
+        <incoming uri="imap+ssl+://imap.qip.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.qip.ru" username="$email" />
+    </provider>
+    <provider id="ruqippochtaimap" label="pochta.ru" domain="pochta.ru">
+        <incoming uri="imap+ssl+://imap.pochta.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.pochta.ru" username="$email" />
+    </provider>
+    <provider id="comqipfromruimap" label="fromru.com" domain="fromru.com">
+        <incoming uri="imap+ssl+://imap.fromru.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.fromru.com" username="$email" />
+    </provider>
+    <provider id="ruqipfrontimap" label="front.ru" domain="front.ru">
+        <incoming uri="imap+ssl+://imap.front.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.front.ru" username="$email" />
+    </provider>
+    <provider id="ruqiphotboximap" label="hotbox.ru" domain="hotbox.ru">
+        <incoming uri="imap+ssl+://imap.hotbox.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.hotbox.ru" username="$email" />
+    </provider>
+    <provider id="ruqiphotmailimap" label="hotmail.ru" domain="hotmail.ru">
+        <incoming uri="imap+ssl+://imap.hotmail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.hotmail.ru" username="$email" />
+    </provider>
+    <provider id="suqipkrovatkaimap" label="krovatka.su" domain="krovatka.su">
+        <incoming uri="imap+ssl+://imap.krovatka.su" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.krovatka.su" username="$email" />
+    </provider>
+    <provider id="ruqiplandimap" label="land.ru" domain="land.ru">
+        <incoming uri="imap+ssl+://imap.land.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.land.ru" username="$email" />
+    </provider>
+    <provider id="comqipmail15imap" label="mail15.com" domain="mail15.com">
+        <incoming uri="imap+ssl+://imap.mail15.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail15.com" username="$email" />
+    </provider>
+    <provider id="comqipmail333imap" label="mail333.com" domain="mail333.com">
+        <incoming uri="imap+ssl+://imap.mail333.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.mail333.com" username="$email" />
+    </provider>
+    <provider id="ruqipnewmailimap" label="newmail.ru" domain="newmail.ru">
+        <incoming uri="imap+ssl+://imap.newmail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.newmail.ru" username="$email" />
+    </provider>
+    <provider id="ruqipnightmailimap" label="nightmail.ru" domain="nightmail.ru">
+        <incoming uri="imap+ssl+://imap.nightmail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.nightmail.ru" username="$email" />
+    </provider>
+    <provider id="ruqipnmimap" label="nm.ru" domain="nm.ru">
+        <incoming uri="imap+ssl+://imap.nm.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.nm.ru" username="$email" />
+    </provider>
+    <provider id="netqippisemimap" label="pisem.net" domain="pisem.net">
+        <incoming uri="imap+ssl+://imap.pisem.net" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.pisem.net" username="$email" />
+    </provider>
+    <provider id="ruqippochtamtimap" label="pochtamt.ru" domain="pochtamt.ru">
+        <incoming uri="imap+ssl+://imap.pochtamt.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.pochtamt.ru" username="$email" />
+    </provider>
+    <provider id="ruqippop3imap" label="pop3.ru" domain="pop3.ru">
+        <incoming uri="imap+ssl+://imap.pop3.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.pop3.ru" username="$email" />
+    </provider>
+    <provider id="ruqiprbcmailimap" label="rbcmail.ru" domain="rbcmail.ru">
+        <incoming uri="imap+ssl+://imap.rbcmail.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.rbcmail.ru" username="$email" />
+    </provider>
+    <provider id="ruqipsmtpimap" label="smtp.ru" domain="smtp.ru">
+        <incoming uri="imap+ssl+://imap.smtp.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.smtp.ru" username="$email" />
+    </provider>
+    <provider id="ruqip5ballovimap" label="5ballov.ru" domain="5ballov.ru">
+        <incoming uri="imap+ssl+://imap.5ballov.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.5ballov.ru" username="$email" />
+    </provider>
+    <provider id="ruqipaeternaimap" label="aeterna.ru" domain="aeterna.ru">
+        <incoming uri="imap+ssl+://imap.aeterna.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aeterna.ru" username="$email" />
+    </provider>
+    <provider id="ruqipzizaimap" label="ziza.ru" domain="ziza.ru">
+        <incoming uri="imap+ssl+://imap.ziza.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.ziza.ru" username="$email" />
+    </provider>
+    <provider id="ruqipmemoriimap" label="memori.ru" domain="memori.ru">
+        <incoming uri="imap+ssl+://imap.memori.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.memori.ru" username="$email" />
+    </provider>
+    <provider id="ruqipphotofileimap" label="photofile.ru" domain="photofile.ru">
+        <incoming uri="imap+ssl+://imap.photofile.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.photofile.ru" username="$email" />
+    </provider>
+    <provider id="ruqipfotoplenkaimap" label="fotoplenka.ru" domain="fotoplenka.ru">
+        <incoming uri="imap+ssl+://imap.fotoplenka.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.fotoplenka.ru" username="$email" />
+    </provider>
+    <provider id="comqippochtaimap" label="pochta.com" domain="pochta.com">
+        <incoming uri="imap+ssl+://imap.pochta.ru" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.pochta.ru" username="$email" />
+    </provider>
+
+    <!-- Slovakia -->
+    <provider id="azet.sk" label="Azet.sk" domain="azet.sk">
+        <incoming uri="imap+ssl+://imap.azet.sk" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.azet.sk" username="$email" />
+    </provider>
+
+    <!-- The Netherlands -->
+    <!-- Ziggo variants -->
+    <provider id="casema.nl" label="Ziggo" domain="casema.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="chello.nl" label="Ziggo" domain="chello.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="hahah.nl" label="Ziggo" domain="hahah.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="home.nl" label="Ziggo" domain="home.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="multiweb.nl" label="Ziggo" domain="multiweb.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="quicknet.nl" label="Ziggo" domain="quicknet.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="razcall.com" label="Ziggo" domain="razcall.com">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="razcall.nl" label="Ziggo" domain="razcall.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="upcmail.nl" label="Ziggo" domain="upcmail.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="zeggis.com" label="Ziggo" domain="zeggis.com">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="zeggis.nl" label="Ziggo" domain="zeggis.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="ziggomail.com" label="Ziggo" domain="ziggomail.com">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="ziggo.nl" label="Ziggo" domain="ziggo.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+    <provider id="zinders.nl" label="Ziggo" domain="zinders.nl">
+        <incoming uri="imap+ssl+://imap.ziggo.nl"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.ziggo.nl" username="$email" />
+    </provider>
+
+    <!-- EU wide -->
+    <provider id="fairnatics.net" label="Fairnatics" domain="fairnatics.net">
+        <incoming uri="imap+ssl+://mail.fairnatics.net" username="$email" />
+        <outgoing uri="smtp+tls+://mail.fairnatics.net:25" username="$email" />
+    </provider>
+
+    <!-- eFoundation -->
+    <provider id="e.foundation" label="/e/" domain="e.email">
+        <incoming uri="imap+ssl+://mail.ecloud.global" username="$email" />
+        <outgoing uri="smtp+tls+://mail.ecloud.global" username="$email" />
+    </provider>
+
+    <!-- AOL variants -->
+    <provider domain="aol.com">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.de">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.it">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.fr">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.es">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.se">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.co.uk">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.co.nz">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.com.au">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.com.ar">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.com.br">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+    <provider domain="aol.com.mx">
+        <incoming uri="imap+ssl+://imap.aol.com" username="$email" />
+        <outgoing uri="smtp+ssl+://smtp.aol.com" username="$email" />
+    </provider>
+
+    <!-- Microsoft variants -->
+    <provider domain="outlook.com">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="hotmail.com">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="msn.com">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="live.com">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="live.co.uk">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="hotmail.co.uk">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+    <provider domain="outlook.sk">
+        <incoming uri="imap+ssl+://outlook.office365.com"  username="$email" />
+        <outgoing uri="smtp+tls+://smtp.office365.com" username="$email" />
+    </provider>
+
+</providers>

app/autodiscovery/providersxml/src/test/java/com/fsck/k9/autodiscovery/providersxml/ProvidersXmlDiscoveryTest.kt

@@ -0,0 +1,64 @@
+package com.fsck.k9.autodiscovery.providersxml
+
+import androidx.test.core.app.ApplicationProvider
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isNotNull
+import assertk.assertions.isNull
+import com.fsck.k9.RobolectricTest
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+import com.fsck.k9.oauth.OAuthConfiguration
+import com.fsck.k9.oauth.OAuthConfigurationProvider
+import org.junit.Test
+
+class ProvidersXmlDiscoveryTest : RobolectricTest() {
+    private val xmlProvider = ProvidersXmlProvider(ApplicationProvider.getApplicationContext())
+    private val oAuthConfigurationProvider = createOAuthConfigurationProvider()
+    private val providersXmlDiscovery = ProvidersXmlDiscovery(xmlProvider, oAuthConfigurationProvider)
+
+    @Test
+    fun discover_withGmailDomain_shouldReturnCorrectSettings() {
+        val connectionSettings = providersXmlDiscovery.discover("user@gmail.com")
+
+        assertThat(connectionSettings).isNotNull()
+        with(connectionSettings!!.incoming.first()) {
+            assertThat(host).isEqualTo("imap.gmail.com")
+            assertThat(security).isEqualTo(ConnectionSecurity.SSL_TLS_REQUIRED)
+            assertThat(authType).isEqualTo(AuthType.XOAUTH2)
+            assertThat(username).isEqualTo("user@gmail.com")
+        }
+        with(connectionSettings.outgoing.first()) {
+            assertThat(host).isEqualTo("smtp.gmail.com")
+            assertThat(security).isEqualTo(ConnectionSecurity.SSL_TLS_REQUIRED)
+            assertThat(authType).isEqualTo(AuthType.XOAUTH2)
+            assertThat(username).isEqualTo("user@gmail.com")
+        }
+    }
+
+    @Test
+    fun discover_withUnknownDomain_shouldReturnNull() {
+        val connectionSettings = providersXmlDiscovery.discover(
+            "user@not.present.in.providers.xml.example"
+        )
+
+        assertThat(connectionSettings).isNull()
+    }
+
+    private fun createOAuthConfigurationProvider(): OAuthConfigurationProvider {
+        val googleConfig = OAuthConfiguration(
+            clientId = "irrelevant",
+            scopes = listOf("irrelevant"),
+            authorizationEndpoint = "irrelevant",
+            tokenEndpoint = "irrelevant",
+            redirectUri = "irrelevant"
+        )
+
+        return OAuthConfigurationProvider(
+            configurations = mapOf(
+                listOf("imap.gmail.com", "smtp.gmail.com") to googleConfig
+            ),
+            googleConfiguration = googleConfig
+        )
+    }
+}

app/autodiscovery/srvrecords/build.gradle.kts

@@ -0,0 +1,11 @@
+@Suppress("DSL_SCOPE_VIOLATION")
+plugins {
+    id(ThunderbirdPlugins.Library.jvm)
+    alias(libs.plugins.android.lint)
+}
+
+dependencies {
+    api(projects.app.autodiscovery.api)
+
+    implementation(libs.minidns.hla)
+}

app/autodiscovery/srvrecords/src/main/java/com/fsck/k9/autodiscovery/srvrecords/MiniDnsSrvResolver.kt

@@ -0,0 +1,29 @@
+package com.fsck.k9.autodiscovery.srvrecords
+
+import com.fsck.k9.mail.ConnectionSecurity.SSL_TLS_REQUIRED
+import com.fsck.k9.mail.ConnectionSecurity.STARTTLS_REQUIRED
+import org.minidns.dnslabel.DnsLabel
+import org.minidns.dnsname.DnsName
+import org.minidns.hla.ResolverApi
+import org.minidns.hla.srv.SrvProto
+
+class MiniDnsSrvResolver : SrvResolver {
+    override fun lookup(domain: String, type: SrvType): List<MailService> {
+        val result = ResolverApi.INSTANCE.resolveSrv(
+            DnsLabel.from(type.label),
+            SrvProto.tcp.dnsLabel,
+            DnsName.from(domain)
+        )
+
+        val security = if (type.assumeTls) SSL_TLS_REQUIRED else STARTTLS_REQUIRED
+        return result.answersOrEmptySet.map {
+            MailService(
+                srvType = type,
+                host = it.target.toString(),
+                port = it.port,
+                priority = it.priority,
+                security = security
+            )
+        }
+    }
+}

app/autodiscovery/srvrecords/src/main/java/com/fsck/k9/autodiscovery/srvrecords/SrvResolver.kt

@@ -0,0 +1,5 @@
+package com.fsck.k9.autodiscovery.srvrecords
+
+interface SrvResolver {
+    fun lookup(domain: String, type: SrvType): List<MailService>
+}

app/autodiscovery/srvrecords/src/main/java/com/fsck/k9/autodiscovery/srvrecords/SrvServiceDiscovery.kt

@@ -0,0 +1,56 @@
+package com.fsck.k9.autodiscovery.srvrecords
+
+import com.fsck.k9.autodiscovery.api.ConnectionSettingsDiscovery
+import com.fsck.k9.autodiscovery.api.DiscoveredServerSettings
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+import com.fsck.k9.helper.EmailHelper
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+
+class SrvServiceDiscovery(
+    private val srvResolver: MiniDnsSrvResolver
+) : ConnectionSettingsDiscovery {
+
+    override fun discover(email: String): DiscoveryResults? {
+        val domain = EmailHelper.getDomainFromEmailAddress(email) ?: return null
+        val mailServicePriority = compareBy<MailService> { it.priority }.thenByDescending { it.security }
+
+        val outgoingSettings = listOf(SrvType.SUBMISSIONS, SrvType.SUBMISSION)
+            .flatMap { srvResolver.lookup(domain, it) }
+            .sortedWith(mailServicePriority)
+            .map { newServerSettings(it, email) }
+
+        val incomingSettings = listOf(SrvType.IMAPS, SrvType.IMAP)
+            .flatMap { srvResolver.lookup(domain, it) }
+            .sortedWith(mailServicePriority)
+            .map { newServerSettings(it, email) }
+
+        return DiscoveryResults(incoming = incomingSettings, outgoing = outgoingSettings)
+    }
+}
+
+fun newServerSettings(service: MailService, email: String): DiscoveredServerSettings {
+    return DiscoveredServerSettings(
+        service.srvType.protocol,
+        service.host,
+        service.port,
+        service.security,
+        AuthType.PLAIN,
+        email
+    )
+}
+
+enum class SrvType(val label: String, val protocol: String, val assumeTls: Boolean) {
+    SUBMISSIONS("_submissions", "smtp", true),
+    SUBMISSION("_submission", "smtp", false),
+    IMAPS("_imaps", "imap", true),
+    IMAP("_imap", "imap", false)
+}
+
+data class MailService(
+    val srvType: SrvType,
+    val host: String,
+    val port: Int,
+    val priority: Int,
+    val security: ConnectionSecurity
+)

app/autodiscovery/srvrecords/src/test/java/com/fsck/k9/autodiscovery/srvrecords/SrvServiceDiscoveryTest.kt

@@ -0,0 +1,178 @@
+package com.fsck.k9.autodiscovery.srvrecords
+
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+import com.fsck.k9.mail.ConnectionSecurity
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.mockito.kotlin.doReturn
+import org.mockito.kotlin.mock
+
+class SrvServiceDiscoveryTest {
+
+    @Test
+    fun discover_whenNoMailServices_shouldReturnNoResults() {
+        val srvResolver = newMockSrvResolver()
+
+        val srvServiceDiscovery = SrvServiceDiscovery(srvResolver)
+        val result = srvServiceDiscovery.discover("test@example.com")
+
+        assertEquals(DiscoveryResults(listOf(), listOf()), result)
+    }
+
+    @Test
+    fun discover_whenNoSMTP_shouldReturnJustIMAP() {
+        val srvResolver = newMockSrvResolver(
+            imapServices = listOf(newMailService(port = 143, srvType = SrvType.IMAP)),
+            imapsServices = listOf(
+                newMailService(port = 993, srvType = SrvType.IMAPS, security = ConnectionSecurity.SSL_TLS_REQUIRED)
+            )
+        )
+
+        val srvServiceDiscovery = SrvServiceDiscovery(srvResolver)
+        val result = srvServiceDiscovery.discover("test@example.com")
+
+        assertEquals(2, result!!.incoming.size)
+        assertEquals(0, result.outgoing.size)
+    }
+
+    @Test
+    fun discover_whenNoIMAP_shouldReturnJustSMTP() {
+        val srvResolver = newMockSrvResolver(
+            submissionServices = listOf(
+                newMailService(
+                    port = 25,
+                    srvType = SrvType.SUBMISSION,
+                    security = ConnectionSecurity.STARTTLS_REQUIRED
+                ),
+                newMailService(
+                    port = 465,
+                    srvType = SrvType.SUBMISSIONS,
+                    security = ConnectionSecurity.SSL_TLS_REQUIRED
+                )
+            )
+        )
+
+        val srvServiceDiscovery = SrvServiceDiscovery(srvResolver)
+        val result = srvServiceDiscovery.discover("test@example.com")
+
+        assertEquals(0, result!!.incoming.size)
+        assertEquals(2, result.outgoing.size)
+    }
+
+    @Test
+    fun discover_withRequiredServices_shouldCorrectlyPrioritize() {
+        val srvResolver = newMockSrvResolver(
+            submissionServices = listOf(
+                newMailService(
+                    host = "smtp1.example.com",
+                    port = 25,
+                    srvType = SrvType.SUBMISSION,
+                    security = ConnectionSecurity.STARTTLS_REQUIRED,
+                    priority = 0
+                ),
+                newMailService(
+                    host = "smtp2.example.com",
+                    port = 25,
+                    srvType = SrvType.SUBMISSION,
+                    security = ConnectionSecurity.STARTTLS_REQUIRED,
+                    priority = 1
+                )
+            ),
+            submissionsServices = listOf(
+                newMailService(
+                    host = "smtp3.example.com",
+                    port = 465,
+                    srvType = SrvType.SUBMISSIONS,
+                    security = ConnectionSecurity.SSL_TLS_REQUIRED,
+                    priority = 0
+                ),
+                newMailService(
+                    host = "smtp4.example.com",
+                    port = 465,
+                    srvType = SrvType.SUBMISSIONS,
+                    security = ConnectionSecurity.SSL_TLS_REQUIRED,
+                    priority = 1
+                )
+            ),
+            imapServices = listOf(
+                newMailService(
+                    host = "imap1.example.com",
+                    port = 143,
+                    srvType = SrvType.IMAP,
+                    security = ConnectionSecurity.STARTTLS_REQUIRED,
+                    priority = 0
+                ),
+                newMailService(
+                    host = "imap2.example.com",
+                    port = 143,
+                    srvType = SrvType.IMAP,
+                    security = ConnectionSecurity.STARTTLS_REQUIRED,
+                    priority = 1
+                )
+            ),
+            imapsServices = listOf(
+                newMailService(
+                    host = "imaps1.example.com",
+                    port = 993,
+                    srvType = SrvType.IMAPS,
+                    security = ConnectionSecurity.SSL_TLS_REQUIRED,
+                    priority = 0
+                ),
+                newMailService(
+                    host = "imaps2.example.com",
+                    port = 993,
+                    srvType = SrvType.IMAPS,
+                    security = ConnectionSecurity.SSL_TLS_REQUIRED,
+                    priority = 1
+                )
+            )
+        )
+
+        val srvServiceDiscovery = SrvServiceDiscovery(srvResolver)
+        val result = srvServiceDiscovery.discover("test@example.com")
+
+        assertEquals(
+            listOf(
+                "smtp3.example.com",
+                "smtp1.example.com",
+                "smtp4.example.com",
+                "smtp2.example.com"
+            ),
+            result?.outgoing?.map { it.host }
+        )
+        assertEquals(
+            listOf(
+                "imaps1.example.com",
+                "imap1.example.com",
+                "imaps2.example.com",
+                "imap2.example.com"
+            ),
+            result?.incoming?.map { it.host }
+        )
+    }
+
+    private fun newMailService(
+        host: String = "example.com",
+        priority: Int = 0,
+        security: ConnectionSecurity = ConnectionSecurity.STARTTLS_REQUIRED,
+        srvType: SrvType,
+        port: Int
+    ): MailService {
+        return MailService(srvType, host, port, priority, security)
+    }
+
+    private fun newMockSrvResolver(
+        host: String = "example.com",
+        submissionServices: List<MailService> = listOf(),
+        submissionsServices: List<MailService> = listOf(),
+        imapServices: List<MailService> = listOf(),
+        imapsServices: List<MailService> = listOf()
+    ): MiniDnsSrvResolver {
+        return mock {
+            on { lookup(host, SrvType.SUBMISSION) } doReturn submissionServices
+            on { lookup(host, SrvType.SUBMISSIONS) } doReturn submissionsServices
+            on { lookup(host, SrvType.IMAP) } doReturn imapServices
+            on { lookup(host, SrvType.IMAPS) } doReturn imapsServices
+        }
+    }
+}

app/autodiscovery/thunderbird/build.gradle.kts

@@ -0,0 +1,15 @@
+@Suppress("DSL_SCOPE_VIOLATION")
+plugins {
+    id(ThunderbirdPlugins.Library.jvm)
+    alias(libs.plugins.android.lint)
+}
+
+dependencies {
+    api(projects.app.autodiscovery.api)
+
+    compileOnly(libs.xmlpull)
+    implementation(libs.okhttp)
+
+    testImplementation(libs.kxml2)
+    testImplementation(libs.okhttp.mockwebserver)
+}

app/autodiscovery/thunderbird/src/main/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigFetcher.kt

@@ -0,0 +1,28 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import com.fsck.k9.logging.Timber
+import java.io.IOException
+import java.io.InputStream
+import okhttp3.HttpUrl
+import okhttp3.OkHttpClient
+import okhttp3.Request
+
+class ThunderbirdAutoconfigFetcher(private val okHttpClient: OkHttpClient) {
+
+    fun fetchAutoconfigFile(url: HttpUrl): InputStream? {
+        return try {
+            val request = Request.Builder().url(url).build()
+
+            val response = okHttpClient.newCall(request).execute()
+
+            if (response.isSuccessful) {
+                response.body?.byteStream()
+            } else {
+                null
+            }
+        } catch (e: IOException) {
+            Timber.d(e, "Error fetching URL: %s", url)
+            null
+        }
+    }
+}

app/autodiscovery/thunderbird/src/main/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigParser.kt

@@ -0,0 +1,102 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import com.fsck.k9.autodiscovery.api.DiscoveredServerSettings
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+import java.io.IOException
+import java.io.InputStream
+import java.io.InputStreamReader
+import org.xmlpull.v1.XmlPullParser
+import org.xmlpull.v1.XmlPullParserException
+import org.xmlpull.v1.XmlPullParserFactory
+
+/**
+ * Parser for Thunderbird's
+ * [Autoconfig file format](https://wiki.mozilla.org/Thunderbird:Autoconfiguration:ConfigFileFormat)
+ */
+class ThunderbirdAutoconfigParser {
+    fun parseSettings(stream: InputStream, email: String): DiscoveryResults? {
+        val factory = XmlPullParserFactory.newInstance()
+        val xpp = factory.newPullParser()
+
+        xpp.setInput(InputStreamReader(stream))
+
+        val incomingServers = mutableListOf<DiscoveredServerSettings>()
+        val outgoingServers = mutableListOf<DiscoveredServerSettings>()
+        var eventType = xpp.eventType
+        while (eventType != XmlPullParser.END_DOCUMENT) {
+            if (eventType == XmlPullParser.START_TAG) {
+                when (xpp.name) {
+                    "incomingServer" -> {
+                        incomingServers += parseServer(xpp, "incomingServer", email)
+                    }
+                    "outgoingServer" -> {
+                        outgoingServers += parseServer(xpp, "outgoingServer", email)
+                    }
+                }
+            }
+            eventType = xpp.next()
+        }
+        return DiscoveryResults(incomingServers, outgoingServers)
+    }
+
+    private fun parseServer(xpp: XmlPullParser, nodeName: String, email: String): DiscoveredServerSettings {
+        val type = xpp.getAttributeValue(null, "type")
+        var host: String? = null
+        var username: String? = null
+        var port: Int? = null
+        var authType: AuthType? = null
+        var connectionSecurity: ConnectionSecurity? = null
+
+        var eventType = xpp.eventType
+        while (!(eventType == XmlPullParser.END_TAG && nodeName == xpp.name)) {
+            if (eventType == XmlPullParser.START_TAG) {
+                when (xpp.name) {
+                    "hostname" -> {
+                        host = getText(xpp)
+                    }
+                    "port" -> {
+                        port = getText(xpp).toInt()
+                    }
+                    "username" -> {
+                        username = getText(xpp).replace("%EMAILADDRESS%", email)
+                    }
+                    "authentication" -> {
+                        if (authType == null) authType = parseAuthType(getText(xpp))
+                    }
+                    "socketType" -> {
+                        connectionSecurity = parseSocketType(getText(xpp))
+                    }
+                }
+            }
+            eventType = xpp.next()
+        }
+
+        return DiscoveredServerSettings(type, host!!, port!!, connectionSecurity!!, authType, username)
+    }
+
+    private fun parseAuthType(authentication: String): AuthType? {
+        return when (authentication) {
+            "password-cleartext" -> AuthType.PLAIN
+            "TLS-client-cert" -> AuthType.EXTERNAL
+            "secure" -> AuthType.CRAM_MD5
+            else -> null
+        }
+    }
+
+    private fun parseSocketType(socketType: String): ConnectionSecurity? {
+        return when (socketType) {
+            "plain" -> ConnectionSecurity.NONE
+            "SSL" -> ConnectionSecurity.SSL_TLS_REQUIRED
+            "STARTTLS" -> ConnectionSecurity.STARTTLS_REQUIRED
+            else -> null
+        }
+    }
+
+    @Throws(XmlPullParserException::class, IOException::class)
+    private fun getText(xpp: XmlPullParser): String {
+        val eventType = xpp.next()
+        return if (eventType != XmlPullParser.TEXT) "" else xpp.text
+    }
+}

app/autodiscovery/thunderbird/src/main/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigUrlProvider.kt

@@ -0,0 +1,47 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import com.fsck.k9.helper.EmailHelper
+import okhttp3.HttpUrl
+import okhttp3.HttpUrl.Companion.toHttpUrl
+
+class ThunderbirdAutoconfigUrlProvider {
+    fun getAutoconfigUrls(email: String): List<HttpUrl> {
+        val domain = EmailHelper.getDomainFromEmailAddress(email)
+        requireNotNull(domain) { "Couldn't extract domain from email address: $email" }
+
+        return listOf(
+            createProviderUrl(domain, email),
+            createDomainUrl(scheme = "https", domain),
+            createDomainUrl(scheme = "http", domain),
+            createIspDbUrl(domain)
+        )
+    }
+
+    private fun createProviderUrl(domain: String?, email: String): HttpUrl {
+        // https://autoconfig.{domain}/mail/config-v1.1.xml?emailaddress={email}
+        return HttpUrl.Builder()
+            .scheme("https")
+            .host("autoconfig.$domain")
+            .addEncodedPathSegments("mail/config-v1.1.xml")
+            .addQueryParameter("emailaddress", email)
+            .build()
+    }
+
+    private fun createDomainUrl(scheme: String, domain: String): HttpUrl {
+        // https://{domain}/.well-known/autoconfig/mail/config-v1.1.xml
+        // http://{domain}/.well-known/autoconfig/mail/config-v1.1.xml
+        return HttpUrl.Builder()
+            .scheme(scheme)
+            .host(domain)
+            .addEncodedPathSegments(".well-known/autoconfig/mail/config-v1.1.xml")
+            .build()
+    }
+
+    private fun createIspDbUrl(domain: String): HttpUrl {
+        // https://autoconfig.thunderbird.net/v1.1/{domain}
+        return "https://autoconfig.thunderbird.net/v1.1/".toHttpUrl()
+            .newBuilder()
+            .addPathSegment(domain)
+            .build()
+    }
+}

app/autodiscovery/thunderbird/src/main/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdDiscovery.kt

@@ -0,0 +1,28 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import com.fsck.k9.autodiscovery.api.ConnectionSettingsDiscovery
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+
+class ThunderbirdDiscovery(
+    private val urlProvider: ThunderbirdAutoconfigUrlProvider,
+    private val fetcher: ThunderbirdAutoconfigFetcher,
+    private val parser: ThunderbirdAutoconfigParser
+) : ConnectionSettingsDiscovery {
+
+    override fun discover(email: String): DiscoveryResults? {
+        val autoconfigUrls = urlProvider.getAutoconfigUrls(email)
+
+        return autoconfigUrls
+            .asSequence()
+            .mapNotNull { autoconfigUrl ->
+                fetcher.fetchAutoconfigFile(autoconfigUrl)?.use { inputStream ->
+                    parser.parseSettings(inputStream, email)
+                }
+            }
+            .firstOrNull { result ->
+                result.incoming.isNotEmpty() || result.outgoing.isNotEmpty()
+            }
+    }
+
+    override fun toString(): String = "Thunderbird autoconfig"
+}

app/autodiscovery/thunderbird/src/test/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigFetcherTest.kt

@@ -0,0 +1,44 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isNull
+import kotlin.test.assertNotNull
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.Test
+
+class ThunderbirdAutoconfigFetcherTest {
+    private val fetcher = ThunderbirdAutoconfigFetcher(OkHttpClient.Builder().build())
+
+    @Test
+    fun shouldHandleNonexistentUrl() {
+        val nonExistentUrl =
+            "https://autoconfig.domain.invalid/mail/config-v1.1.xml?emailaddress=test%40domain.example".toHttpUrl()
+
+        val inputStream = fetcher.fetchAutoconfigFile(nonExistentUrl)
+
+        assertThat(inputStream).isNull()
+    }
+
+    @Test
+    fun shouldHandleEmptyResponse() {
+        val server = MockWebServer().apply {
+            this.enqueue(
+                MockResponse()
+                    .setBody("")
+                    .setResponseCode(204),
+            )
+            start()
+        }
+        val url = server.url("/empty/")
+
+        val inputStream = fetcher.fetchAutoconfigFile(url)
+
+        assertNotNull(inputStream) { inputStream ->
+            assertThat(inputStream.available()).isEqualTo(0)
+        }
+    }
+}

app/autodiscovery/thunderbird/src/test/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigTest.kt

@@ -0,0 +1,174 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isNotNull
+import com.fsck.k9.autodiscovery.api.DiscoveredServerSettings
+import com.fsck.k9.autodiscovery.api.DiscoveryResults
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+import org.junit.Test
+
+class ThunderbirdAutoconfigTest {
+    private val parser = ThunderbirdAutoconfigParser()
+
+    @Test
+    fun settingsExtract() {
+        val input =
+            """
+            <?xml version="1.0"?>
+            <clientConfig version="1.1">
+                <emailProvider id="metacode.biz">
+                    <domain>metacode.biz</domain>
+    
+                    <incomingServer type="imap">
+                        <hostname>imap.googlemail.com</hostname>
+                        <port>993</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                    </incomingServer>
+    
+                    <outgoingServer type="smtp">
+                        <hostname>smtp.googlemail.com</hostname>
+                        <port>465</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                        <addThisServer>true</addThisServer>
+                    </outgoingServer>
+                </emailProvider>
+            </clientConfig>
+            """.trimIndent().byteInputStream()
+
+        val connectionSettings = parser.parseSettings(input, "test@metacode.biz")
+
+        assertThat(connectionSettings).isNotNull()
+        assertThat(connectionSettings!!.incoming).isNotNull()
+        assertThat(connectionSettings.outgoing).isNotNull()
+        with(connectionSettings.incoming.first()) {
+            assertThat(host).isEqualTo("imap.googlemail.com")
+            assertThat(port).isEqualTo(993)
+            assertThat(username).isEqualTo("test@metacode.biz")
+        }
+        with(connectionSettings.outgoing.first()) {
+            assertThat(host).isEqualTo("smtp.googlemail.com")
+            assertThat(port).isEqualTo(465)
+            assertThat(username).isEqualTo("test@metacode.biz")
+        }
+    }
+
+    @Test
+    fun multipleServers() {
+        val input =
+            """
+            <?xml version="1.0"?>
+            <clientConfig version="1.1">
+                <emailProvider id="metacode.biz">
+                    <domain>metacode.biz</domain>
+    
+                    <incomingServer type="imap">
+                        <hostname>imap.googlemail.com</hostname>
+                        <port>993</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                    </incomingServer>
+    
+                    <outgoingServer type="smtp">
+                        <hostname>first</hostname>
+                        <port>465</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                        <addThisServer>true</addThisServer>
+                    </outgoingServer>
+    
+                    <outgoingServer type="smtp">
+                        <hostname>second</hostname>
+                        <port>465</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                        <addThisServer>true</addThisServer>
+                    </outgoingServer>
+                </emailProvider>
+            </clientConfig>
+            """.trimIndent().byteInputStream()
+
+        val discoveryResults = parser.parseSettings(input, "test@metacode.biz")
+
+        assertThat(discoveryResults).isNotNull()
+        assertThat(discoveryResults!!.outgoing).isNotNull()
+        with(discoveryResults.outgoing[0]) {
+            assertThat(host).isEqualTo("first")
+            assertThat(port).isEqualTo(465)
+            assertThat(username).isEqualTo("test@metacode.biz")
+        }
+        with(discoveryResults.outgoing[1]) {
+            assertThat(host).isEqualTo("second")
+            assertThat(port).isEqualTo(465)
+            assertThat(username).isEqualTo("test@metacode.biz")
+        }
+    }
+
+    @Test
+    fun invalidResponse() {
+        val input =
+            """
+            <?xml version="1.0"?>
+                <clientConfig version="1.1">
+                    <emailProvider id="metacode.biz">
+                        <domain>metacode.biz</domain>
+            """.trimIndent().byteInputStream()
+
+        val connectionSettings = parser.parseSettings(input, "test@metacode.biz")
+
+        assertThat(connectionSettings).isEqualTo(DiscoveryResults(listOf(), listOf()))
+    }
+
+    @Test
+    fun incompleteConfiguration() {
+        val input =
+            """
+            <?xml version="1.0"?>
+            <clientConfig version="1.1">
+                <emailProvider id="metacode.biz">
+                    <domain>metacode.biz</domain>
+    
+                    <incomingServer type="imap">
+                        <hostname>imap.googlemail.com</hostname>
+                        <port>993</port>
+                        <socketType>SSL</socketType>
+                        <username>%EMAILADDRESS%</username>
+                        <authentication>OAuth2</authentication>
+                        <authentication>password-cleartext</authentication>
+                    </incomingServer>
+                </emailProvider>
+            </clientConfig>
+            """.trimIndent().byteInputStream()
+
+        val connectionSettings = parser.parseSettings(input, "test@metacode.biz")
+
+        assertThat(connectionSettings).isEqualTo(
+            DiscoveryResults(
+                listOf(
+                    DiscoveredServerSettings(
+                        protocol = "imap",
+                        host = "imap.googlemail.com",
+                        port = 993,
+                        security = ConnectionSecurity.SSL_TLS_REQUIRED,
+                        authType = AuthType.PLAIN,
+                        username = "test@metacode.biz"
+                    )
+                ),
+                listOf()
+            )
+        )
+    }
+}

app/autodiscovery/thunderbird/src/test/java/com/fsck/k9/autodiscovery/thunderbird/ThunderbirdAutoconfigUrlProviderTest.kt

@@ -0,0 +1,21 @@
+package com.fsck.k9.autodiscovery.thunderbird
+
+import assertk.assertThat
+import assertk.assertions.containsExactly
+import org.junit.Test
+
+class ThunderbirdAutoconfigUrlProviderTest {
+    private val urlProvider = ThunderbirdAutoconfigUrlProvider()
+
+    @Test
+    fun `getAutoconfigUrls with ASCII email address`() {
+        val autoconfigUrls = urlProvider.getAutoconfigUrls("test@domain.example")
+
+        assertThat(autoconfigUrls.map { it.toString() }).containsExactly(
+            "https://autoconfig.domain.example/mail/config-v1.1.xml?emailaddress=test%40domain.example",
+            "https://domain.example/.well-known/autoconfig/mail/config-v1.1.xml",
+            "http://domain.example/.well-known/autoconfig/mail/config-v1.1.xml",
+            "https://autoconfig.thunderbird.net/v1.1/domain.example"
+        )
+    }
+}

app/core/build.gradle.kts

@@ -0,0 +1,51 @@
+@Suppress("DSL_SCOPE_VIOLATION")
+plugins {
+    id(ThunderbirdPlugins.Library.android)
+    alias(libs.plugins.kotlin.parcelize)
+}
+
+dependencies {
+    api(projects.mail.common)
+    api(projects.backend.api)
+    api(projects.app.htmlCleaner)
+    api(projects.core.android.common)
+
+    implementation(projects.plugins.openpgpApiLib.openpgpApi)
+
+    api(libs.koin.android)
+
+    api(libs.androidx.annotation)
+
+    implementation(libs.okio)
+    implementation(libs.commons.io)
+    implementation(libs.androidx.core.ktx)
+    implementation(libs.androidx.work.ktx)
+    implementation(libs.androidx.fragment)
+    implementation(libs.androidx.localbroadcastmanager)
+    implementation(libs.jsoup)
+    implementation(libs.moshi)
+    implementation(libs.timber)
+    implementation(libs.mime4j.core)
+    implementation(libs.mime4j.dom)
+
+    testApi(projects.core.testing)
+    testImplementation(projects.mail.testing)
+    testImplementation(projects.backend.imap)
+    testImplementation(projects.mail.protocols.smtp)
+    testImplementation(projects.app.storage)
+    testImplementation(projects.app.testing)
+
+    testImplementation(libs.kotlin.test)
+    testImplementation(libs.kotlin.reflect)
+    testImplementation(libs.robolectric)
+    testImplementation(libs.androidx.test.core)
+    testImplementation(libs.jdom2)
+}
+
+android {
+    namespace = "com.fsck.k9.core"
+
+    buildFeatures {
+        buildConfig = true
+    }
+}

app/core/src/main/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
+    <uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
+
+</manifest>

app/core/src/main/java/com/fsck/k9/Account.kt

@@ -0,0 +1,696 @@
+package com.fsck.k9
+
+import com.fsck.k9.backend.api.SyncConfig.ExpungePolicy
+import com.fsck.k9.mail.Address
+import com.fsck.k9.mail.ServerSettings
+import java.util.Calendar
+import java.util.Date
+
+/**
+ * Account stores all of the settings for a single account defined by the user. Each account is defined by a UUID.
+ */
+class Account(override val uuid: String) : BaseAccount {
+    @get:Synchronized
+    @set:Synchronized
+    var deletePolicy = DeletePolicy.NEVER
+
+    @get:Synchronized
+    @set:Synchronized
+    private var internalIncomingServerSettings: ServerSettings? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    private var internalOutgoingServerSettings: ServerSettings? = null
+
+    var incomingServerSettings: ServerSettings
+        get() = internalIncomingServerSettings ?: error("Incoming server settings not set yet")
+        set(value) {
+            internalIncomingServerSettings = value
+        }
+
+    var outgoingServerSettings: ServerSettings
+        get() = internalOutgoingServerSettings ?: error("Outgoing server settings not set yet")
+        set(value) {
+            internalOutgoingServerSettings = value
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var oAuthState: String? = null
+
+    /**
+     * Storage provider ID, used to locate and manage the underlying DB/file storage.
+     */
+    @get:Synchronized
+    @set:Synchronized
+    var localStorageProviderId: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    override var name: String? = null
+        set(value) {
+            field = value?.takeIf { it.isNotEmpty() }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var alwaysBcc: String? = null
+
+    /**
+     * -1 for never.
+     */
+    @get:Synchronized
+    @set:Synchronized
+    var automaticCheckIntervalMinutes = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var displayCount = 0
+        set(value) {
+            if (field != value) {
+                field = value.takeIf { it != -1 } ?: K9.DEFAULT_VISIBLE_LIMIT
+                isChangedVisibleLimits = true
+            }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var chipColor = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifyNewMail = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderNotifyNewMailMode = FolderMode.ALL
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifySelfNewMail = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifyContactsMailOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isIgnoreChatMessages = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var legacyInboxFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedDraftsFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedSentFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedTrashFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedArchiveFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedSpamFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var inboxFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var outboxFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var draftsFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var sentFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var trashFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var archiveFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var spamFolderId: Long? = null
+
+    @get:Synchronized
+    var draftsFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var sentFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var trashFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var archiveFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var spamFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedAutoExpandFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var autoExpandFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderDisplayMode = FolderMode.NOT_SECOND_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderSyncMode = FolderMode.FIRST_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderPushMode = FolderMode.NONE
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderTargetMode = FolderMode.NOT_SECOND_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var accountNumber = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifySync = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var sortType: SortType = SortType.SORT_DATE
+
+    private val sortAscending: MutableMap<SortType, Boolean> = mutableMapOf()
+
+    @get:Synchronized
+    @set:Synchronized
+    var showPictures = ShowPictures.NEVER
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSignatureBeforeQuotedText = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var expungePolicy = Expunge.EXPUNGE_IMMEDIATELY
+
+    @get:Synchronized
+    @set:Synchronized
+    var maxPushFolders = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var idleRefreshMinutes = 0
+
+    @get:JvmName("useCompression")
+    @get:Synchronized
+    @set:Synchronized
+    var useCompression = true
+
+    @get:Synchronized
+    @set:Synchronized
+    var searchableFolders = Searchable.ALL
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSubscribedFoldersOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var maximumPolledMessageAge = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var maximumAutoDownloadMessageSize = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var messageFormat = MessageFormat.HTML
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMessageFormatAuto = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMessageReadReceipt = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var quoteStyle = QuoteStyle.PREFIX
+
+    @get:Synchronized
+    @set:Synchronized
+    var quotePrefix: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var isDefaultQuotedTextShown = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isReplyAfterQuote = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isStripSignature = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSyncRemoteDeletions = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var openPgpProvider: String? = null
+        set(value) {
+            field = value?.takeIf { it.isNotEmpty() }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var openPgpKey: Long = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var autocryptPreferEncryptMutual = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpHideSignOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpEncryptSubject = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpEncryptAllDrafts = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMarkMessageAsReadOnView = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMarkMessageAsReadOnDelete = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isAlwaysShowCcBcc = false
+
+    // Temporarily disabled
+    @get:Synchronized
+    @set:Synchronized
+    var isRemoteSearchFullText = false
+        get() = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var remoteSearchNumResults = 0
+        set(value) {
+            field = value.coerceAtLeast(0)
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var isUploadSentMessages = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var lastSyncTime: Long = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var lastFolderListRefreshTime: Long = 0
+
+    @get:Synchronized
+    var isFinishedSetup = false
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var messagesNotificationChannelVersion = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isChangedVisibleLimits = false
+        private set
+
+    /**
+     * Database ID of the folder that was last selected for a copy or move operation.
+     *
+     * Note: For now this value isn't persisted. So it will be reset when K-9 Mail is restarted.
+     */
+    @get:Synchronized
+    var lastSelectedFolderId: Long? = null
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var identities: MutableList<Identity> = mutableListOf()
+        set(value) {
+            field = value.toMutableList()
+        }
+
+    @get:Synchronized
+    var notificationSettings = NotificationSettings()
+        private set
+
+    val displayName: String
+        get() = name ?: email
+
+    @get:Synchronized
+    @set:Synchronized
+    override var email: String
+        get() = identities[0].email!!
+        set(email) {
+            val newIdentity = identities[0].withEmail(email)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var senderName: String?
+        get() = identities[0].name
+        set(name) {
+            val newIdentity = identities[0].withName(name)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var signatureUse: Boolean
+        get() = identities[0].signatureUse
+        set(signatureUse) {
+            val newIdentity = identities[0].withSignatureUse(signatureUse)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var signature: String?
+        get() = identities[0].signature
+        set(signature) {
+            val newIdentity = identities[0].withSignature(signature)
+            identities[0] = newIdentity
+        }
+
+    @get:JvmName("shouldMigrateToOAuth")
+    @get:Synchronized
+    @set:Synchronized
+    var shouldMigrateToOAuth = false
+
+    /**
+     * @param automaticCheckIntervalMinutes or -1 for never.
+     */
+    @Synchronized
+    fun updateAutomaticCheckIntervalMinutes(automaticCheckIntervalMinutes: Int): Boolean {
+        val oldInterval = this.automaticCheckIntervalMinutes
+        this.automaticCheckIntervalMinutes = automaticCheckIntervalMinutes
+
+        return oldInterval != automaticCheckIntervalMinutes
+    }
+
+    @Synchronized
+    fun setDraftsFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        draftsFolderId = folderId
+        draftsFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasDraftsFolder(): Boolean {
+        return draftsFolderId != null
+    }
+
+    @Synchronized
+    fun setSentFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        sentFolderId = folderId
+        sentFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasSentFolder(): Boolean {
+        return sentFolderId != null
+    }
+
+    @Synchronized
+    fun setTrashFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        trashFolderId = folderId
+        trashFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasTrashFolder(): Boolean {
+        return trashFolderId != null
+    }
+
+    @Synchronized
+    fun setArchiveFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        archiveFolderId = folderId
+        archiveFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasArchiveFolder(): Boolean {
+        return archiveFolderId != null
+    }
+
+    @Synchronized
+    fun setSpamFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        spamFolderId = folderId
+        spamFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasSpamFolder(): Boolean {
+        return spamFolderId != null
+    }
+
+    @Synchronized
+    fun updateFolderSyncMode(syncMode: FolderMode): Boolean {
+        val oldSyncMode = folderSyncMode
+        folderSyncMode = syncMode
+
+        return (oldSyncMode == FolderMode.NONE && syncMode != FolderMode.NONE) ||
+            (oldSyncMode != FolderMode.NONE && syncMode == FolderMode.NONE)
+    }
+
+    @Synchronized
+    fun isSortAscending(sortType: SortType): Boolean {
+        return sortAscending.getOrPut(sortType) { sortType.isDefaultAscending }
+    }
+
+    @Synchronized
+    fun setSortAscending(sortType: SortType, sortAscending: Boolean) {
+        this.sortAscending[sortType] = sortAscending
+    }
+
+    @Synchronized
+    fun replaceIdentities(identities: List<Identity>) {
+        this.identities = identities.toMutableList()
+    }
+
+    @Synchronized
+    fun getIdentity(index: Int): Identity {
+        if (index !in identities.indices) error("Identity with index $index not found")
+
+        return identities[index]
+    }
+
+    fun isAnIdentity(addresses: Array<Address>?): Boolean {
+        if (addresses == null) return false
+
+        return addresses.any { address -> isAnIdentity(address) }
+    }
+
+    fun isAnIdentity(address: Address): Boolean {
+        return findIdentity(address) != null
+    }
+
+    @Synchronized
+    fun findIdentity(address: Address): Identity? {
+        return identities.find { identity ->
+            identity.email.equals(address.address, ignoreCase = true)
+        }
+    }
+
+    val earliestPollDate: Date?
+        get() {
+            val age = maximumPolledMessageAge.takeIf { it >= 0 } ?: return null
+
+            val now = Calendar.getInstance()
+            now[Calendar.HOUR_OF_DAY] = 0
+            now[Calendar.MINUTE] = 0
+            now[Calendar.SECOND] = 0
+            now[Calendar.MILLISECOND] = 0
+
+            if (age < 28) {
+                now.add(Calendar.DATE, age * -1)
+            } else {
+                when (age) {
+                    28 -> now.add(Calendar.MONTH, -1)
+                    56 -> now.add(Calendar.MONTH, -2)
+                    84 -> now.add(Calendar.MONTH, -3)
+                    168 -> now.add(Calendar.MONTH, -6)
+                    365 -> now.add(Calendar.YEAR, -1)
+                }
+            }
+
+            return now.time
+        }
+
+    val isOpenPgpProviderConfigured: Boolean
+        get() = openPgpProvider != null
+
+    @Synchronized
+    fun hasOpenPgpKey(): Boolean {
+        return openPgpKey != NO_OPENPGP_KEY
+    }
+
+    @Synchronized
+    fun setLastSelectedFolderId(folderId: Long) {
+        lastSelectedFolderId = folderId
+    }
+
+    @Synchronized
+    fun resetChangeMarkers() {
+        isChangedVisibleLimits = false
+    }
+
+    @Synchronized
+    fun markSetupFinished() {
+        isFinishedSetup = true
+    }
+
+    @Synchronized
+    fun updateNotificationSettings(block: (oldNotificationSettings: NotificationSettings) -> NotificationSettings) {
+        notificationSettings = block(notificationSettings)
+    }
+
+    override fun toString(): String {
+        return if (K9.isSensitiveDebugLoggingEnabled) displayName else uuid
+    }
+
+    override fun equals(other: Any?): Boolean {
+        return if (other is Account) {
+            other.uuid == uuid
+        } else {
+            super.equals(other)
+        }
+    }
+
+    override fun hashCode(): Int {
+        return uuid.hashCode()
+    }
+
+    enum class FolderMode {
+        NONE,
+        ALL,
+        FIRST_CLASS,
+        FIRST_AND_SECOND_CLASS,
+        NOT_SECOND_CLASS
+    }
+
+    enum class SpecialFolderSelection {
+        AUTOMATIC,
+        MANUAL
+    }
+
+    enum class ShowPictures {
+        NEVER,
+        ALWAYS,
+        ONLY_FROM_CONTACTS
+    }
+
+    enum class Searchable {
+        ALL,
+        DISPLAYABLE,
+        NONE
+    }
+
+    enum class QuoteStyle {
+        PREFIX,
+        HEADER
+    }
+
+    enum class MessageFormat {
+        TEXT,
+        HTML,
+        AUTO
+    }
+
+    enum class Expunge {
+        EXPUNGE_IMMEDIATELY,
+        EXPUNGE_MANUALLY,
+        EXPUNGE_ON_POLL;
+
+        fun toBackendExpungePolicy(): ExpungePolicy = when (this) {
+            EXPUNGE_IMMEDIATELY -> ExpungePolicy.IMMEDIATELY
+            EXPUNGE_MANUALLY -> ExpungePolicy.MANUALLY
+            EXPUNGE_ON_POLL -> ExpungePolicy.ON_POLL
+        }
+    }
+
+    enum class DeletePolicy(@JvmField val setting: Int) {
+        NEVER(0),
+        SEVEN_DAYS(1),
+        ON_DELETE(2),
+        MARK_AS_READ(3);
+
+        companion object {
+            fun fromInt(initialSetting: Int): DeletePolicy {
+                return values().find { it.setting == initialSetting } ?: error("DeletePolicy $initialSetting unknown")
+            }
+        }
+    }
+
+    enum class SortType(val isDefaultAscending: Boolean) {
+        SORT_DATE(false),
+        SORT_ARRIVAL(false),
+        SORT_SUBJECT(true),
+        SORT_SENDER(true),
+        SORT_UNREAD(true),
+        SORT_FLAGGED(true),
+        SORT_ATTACHMENT(true);
+    }
+
+    companion object {
+        /**
+         * Fixed name of outbox - not actually displayed.
+         */
+        const val OUTBOX_NAME = "Outbox"
+
+        @JvmField
+        val DEFAULT_SORT_TYPE = SortType.SORT_DATE
+        const val DEFAULT_SORT_ASCENDING = false
+        const val NO_OPENPGP_KEY: Long = 0
+        const val UNASSIGNED_ACCOUNT_NUMBER = -1
+        const val INTERVAL_MINUTES_NEVER = -1
+        const val DEFAULT_SYNC_INTERVAL = 60
+    }
+}

app/core/src/main/java/com/fsck/k9/AccountPreferenceSerializer.kt

@@ -0,0 +1,648 @@
+package com.fsck.k9
+
+import com.fsck.k9.Account.Companion.DEFAULT_SORT_ASCENDING
+import com.fsck.k9.Account.Companion.DEFAULT_SORT_TYPE
+import com.fsck.k9.Account.Companion.DEFAULT_SYNC_INTERVAL
+import com.fsck.k9.Account.Companion.NO_OPENPGP_KEY
+import com.fsck.k9.Account.Companion.UNASSIGNED_ACCOUNT_NUMBER
+import com.fsck.k9.Account.DeletePolicy
+import com.fsck.k9.Account.Expunge
+import com.fsck.k9.Account.FolderMode
+import com.fsck.k9.Account.MessageFormat
+import com.fsck.k9.Account.QuoteStyle
+import com.fsck.k9.Account.Searchable
+import com.fsck.k9.Account.ShowPictures
+import com.fsck.k9.Account.SortType
+import com.fsck.k9.Account.SpecialFolderSelection
+import com.fsck.k9.helper.Utility
+import com.fsck.k9.mailstore.StorageManager
+import com.fsck.k9.preferences.Storage
+import com.fsck.k9.preferences.StorageEditor
+import timber.log.Timber
+
+class AccountPreferenceSerializer(
+    private val storageManager: StorageManager,
+    private val resourceProvider: CoreResourceProvider,
+    private val serverSettingsSerializer: ServerSettingsSerializer
+) {
+
+    @Synchronized
+    fun loadAccount(account: Account, storage: Storage) {
+        val accountUuid = account.uuid
+        with(account) {
+            incomingServerSettings = serverSettingsSerializer.deserialize(
+                storage.getString("$accountUuid.$INCOMING_SERVER_SETTINGS_KEY", "")
+            )
+            outgoingServerSettings = serverSettingsSerializer.deserialize(
+                storage.getString("$accountUuid.$OUTGOING_SERVER_SETTINGS_KEY", "")
+            )
+            oAuthState = storage.getString("$accountUuid.oAuthState", null)
+            localStorageProviderId = storage.getString("$accountUuid.localStorageProvider", storageManager.defaultProviderId)
+            name = storage.getString("$accountUuid.description", null)
+            alwaysBcc = storage.getString("$accountUuid.alwaysBcc", alwaysBcc)
+            automaticCheckIntervalMinutes = storage.getInt("$accountUuid.automaticCheckIntervalMinutes", DEFAULT_SYNC_INTERVAL)
+            idleRefreshMinutes = storage.getInt("$accountUuid.idleRefreshMinutes", 24)
+            displayCount = storage.getInt("$accountUuid.displayCount", K9.DEFAULT_VISIBLE_LIMIT)
+            if (displayCount < 0) {
+                displayCount = K9.DEFAULT_VISIBLE_LIMIT
+            }
+            isNotifyNewMail = storage.getBoolean("$accountUuid.notifyNewMail", false)
+
+            folderNotifyNewMailMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderNotifyNewMailMode", FolderMode.ALL)
+            isNotifySelfNewMail = storage.getBoolean("$accountUuid.notifySelfNewMail", true)
+            isNotifyContactsMailOnly = storage.getBoolean("$accountUuid.notifyContactsMailOnly", false)
+            isIgnoreChatMessages = storage.getBoolean("$accountUuid.ignoreChatMessages", false)
+            isNotifySync = storage.getBoolean("$accountUuid.notifyMailCheck", false)
+            messagesNotificationChannelVersion = storage.getInt("$accountUuid.messagesNotificationChannelVersion", 0)
+            deletePolicy = DeletePolicy.fromInt(storage.getInt("$accountUuid.deletePolicy", DeletePolicy.NEVER.setting))
+            legacyInboxFolder = storage.getString("$accountUuid.inboxFolderName", null)
+            importedDraftsFolder = storage.getString("$accountUuid.draftsFolderName", null)
+            importedSentFolder = storage.getString("$accountUuid.sentFolderName", null)
+            importedTrashFolder = storage.getString("$accountUuid.trashFolderName", null)
+            importedArchiveFolder = storage.getString("$accountUuid.archiveFolderName", null)
+            importedSpamFolder = storage.getString("$accountUuid.spamFolderName", null)
+
+            inboxFolderId = storage.getString("$accountUuid.inboxFolderId", null)?.toLongOrNull()
+            outboxFolderId = storage.getString("$accountUuid.outboxFolderId", null)?.toLongOrNull()
+
+            val draftsFolderId = storage.getString("$accountUuid.draftsFolderId", null)?.toLongOrNull()
+            val draftsFolderSelection = getEnumStringPref<SpecialFolderSelection>(
+                storage,
+                "$accountUuid.draftsFolderSelection",
+                SpecialFolderSelection.AUTOMATIC
+            )
+            setDraftsFolderId(draftsFolderId, draftsFolderSelection)
+
+            val sentFolderId = storage.getString("$accountUuid.sentFolderId", null)?.toLongOrNull()
+            val sentFolderSelection = getEnumStringPref<SpecialFolderSelection>(
+                storage,
+                "$accountUuid.sentFolderSelection",
+                SpecialFolderSelection.AUTOMATIC
+            )
+            setSentFolderId(sentFolderId, sentFolderSelection)
+
+            val trashFolderId = storage.getString("$accountUuid.trashFolderId", null)?.toLongOrNull()
+            val trashFolderSelection = getEnumStringPref<SpecialFolderSelection>(
+                storage,
+                "$accountUuid.trashFolderSelection",
+                SpecialFolderSelection.AUTOMATIC
+            )
+            setTrashFolderId(trashFolderId, trashFolderSelection)
+
+            val archiveFolderId = storage.getString("$accountUuid.archiveFolderId", null)?.toLongOrNull()
+            val archiveFolderSelection = getEnumStringPref<SpecialFolderSelection>(
+                storage,
+                "$accountUuid.archiveFolderSelection",
+                SpecialFolderSelection.AUTOMATIC
+            )
+            setArchiveFolderId(archiveFolderId, archiveFolderSelection)
+
+            val spamFolderId = storage.getString("$accountUuid.spamFolderId", null)?.toLongOrNull()
+            val spamFolderSelection = getEnumStringPref<SpecialFolderSelection>(
+                storage,
+                "$accountUuid.spamFolderSelection",
+                SpecialFolderSelection.AUTOMATIC
+            )
+            setSpamFolderId(spamFolderId, spamFolderSelection)
+
+            autoExpandFolderId = storage.getString("$accountUuid.autoExpandFolderId", null)?.toLongOrNull()
+
+            expungePolicy = getEnumStringPref<Expunge>(storage, "$accountUuid.expungePolicy", Expunge.EXPUNGE_IMMEDIATELY)
+            isSyncRemoteDeletions = storage.getBoolean("$accountUuid.syncRemoteDeletions", true)
+
+            maxPushFolders = storage.getInt("$accountUuid.maxPushFolders", 10)
+            isSubscribedFoldersOnly = storage.getBoolean("$accountUuid.subscribedFoldersOnly", false)
+            maximumPolledMessageAge = storage.getInt("$accountUuid.maximumPolledMessageAge", -1)
+            maximumAutoDownloadMessageSize = storage.getInt("$accountUuid.maximumAutoDownloadMessageSize", 32768)
+            messageFormat = getEnumStringPref<MessageFormat>(storage, "$accountUuid.messageFormat", DEFAULT_MESSAGE_FORMAT)
+            val messageFormatAuto = storage.getBoolean("$accountUuid.messageFormatAuto", DEFAULT_MESSAGE_FORMAT_AUTO)
+            if (messageFormatAuto && messageFormat == MessageFormat.TEXT) {
+                messageFormat = MessageFormat.AUTO
+            }
+            isMessageReadReceipt = storage.getBoolean("$accountUuid.messageReadReceipt", DEFAULT_MESSAGE_READ_RECEIPT)
+            quoteStyle = getEnumStringPref<QuoteStyle>(storage, "$accountUuid.quoteStyle", DEFAULT_QUOTE_STYLE)
+            quotePrefix = storage.getString("$accountUuid.quotePrefix", DEFAULT_QUOTE_PREFIX)
+            isDefaultQuotedTextShown = storage.getBoolean("$accountUuid.defaultQuotedTextShown", DEFAULT_QUOTED_TEXT_SHOWN)
+            isReplyAfterQuote = storage.getBoolean("$accountUuid.replyAfterQuote", DEFAULT_REPLY_AFTER_QUOTE)
+            isStripSignature = storage.getBoolean("$accountUuid.stripSignature", DEFAULT_STRIP_SIGNATURE)
+            useCompression = storage.getBoolean("$accountUuid.useCompression", true)
+
+            importedAutoExpandFolder = storage.getString("$accountUuid.autoExpandFolderName", null)
+
+            accountNumber = storage.getInt("$accountUuid.accountNumber", UNASSIGNED_ACCOUNT_NUMBER)
+
+            chipColor = storage.getInt("$accountUuid.chipColor", FALLBACK_ACCOUNT_COLOR)
+
+            sortType = getEnumStringPref<SortType>(storage, "$accountUuid.sortTypeEnum", SortType.SORT_DATE)
+
+            setSortAscending(sortType, storage.getBoolean("$accountUuid.sortAscending", false))
+
+            showPictures = getEnumStringPref<ShowPictures>(storage, "$accountUuid.showPicturesEnum", ShowPictures.NEVER)
+
+            updateNotificationSettings {
+                NotificationSettings(
+                    isRingEnabled = storage.getBoolean("$accountUuid.ring", true),
+                    ringtone = storage.getString("$accountUuid.ringtone", DEFAULT_RINGTONE_URI),
+                    light = getEnumStringPref(storage, "$accountUuid.notificationLight", NotificationLight.Disabled),
+                    vibration = NotificationVibration(
+                        isEnabled = storage.getBoolean("$accountUuid.vibrate", false),
+                        pattern = VibratePattern.deserialize(storage.getInt("$accountUuid.vibratePattern", 0)),
+                        repeatCount = storage.getInt("$accountUuid.vibrateTimes", 5)
+                    )
+                )
+            }
+
+            folderDisplayMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderDisplayMode", FolderMode.NOT_SECOND_CLASS)
+
+            folderSyncMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderSyncMode", FolderMode.FIRST_CLASS)
+
+            folderPushMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderPushMode", FolderMode.NONE)
+
+            folderTargetMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderTargetMode", FolderMode.NOT_SECOND_CLASS)
+
+            searchableFolders = getEnumStringPref<Searchable>(storage, "$accountUuid.searchableFolders", Searchable.ALL)
+
+            isSignatureBeforeQuotedText = storage.getBoolean("$accountUuid.signatureBeforeQuotedText", false)
+            replaceIdentities(loadIdentities(accountUuid, storage))
+
+            openPgpProvider = storage.getString("$accountUuid.openPgpProvider", "")
+            openPgpKey = storage.getLong("$accountUuid.cryptoKey", NO_OPENPGP_KEY)
+            isOpenPgpHideSignOnly = storage.getBoolean("$accountUuid.openPgpHideSignOnly", true)
+            isOpenPgpEncryptSubject = storage.getBoolean("$accountUuid.openPgpEncryptSubject", true)
+            isOpenPgpEncryptAllDrafts = storage.getBoolean("$accountUuid.openPgpEncryptAllDrafts", true)
+            autocryptPreferEncryptMutual = storage.getBoolean("$accountUuid.autocryptMutualMode", false)
+            isRemoteSearchFullText = storage.getBoolean("$accountUuid.remoteSearchFullText", false)
+            remoteSearchNumResults = storage.getInt("$accountUuid.remoteSearchNumResults", DEFAULT_REMOTE_SEARCH_NUM_RESULTS)
+            isUploadSentMessages = storage.getBoolean("$accountUuid.uploadSentMessages", true)
+
+            isMarkMessageAsReadOnView = storage.getBoolean("$accountUuid.markMessageAsReadOnView", true)
+            isMarkMessageAsReadOnDelete = storage.getBoolean("$accountUuid.markMessageAsReadOnDelete", true)
+            isAlwaysShowCcBcc = storage.getBoolean("$accountUuid.alwaysShowCcBcc", false)
+            lastSyncTime = storage.getLong("$accountUuid.lastSyncTime", 0L)
+            lastFolderListRefreshTime = storage.getLong("$accountUuid.lastFolderListRefreshTime", 0L)
+
+            shouldMigrateToOAuth = storage.getBoolean("$accountUuid.migrateToOAuth", false)
+
+            val isFinishedSetup = storage.getBoolean("$accountUuid.isFinishedSetup", true)
+            if (isFinishedSetup) markSetupFinished()
+
+            resetChangeMarkers()
+        }
+    }
+
+    @Synchronized
+    private fun loadIdentities(accountUuid: String, storage: Storage): List<Identity> {
+        val newIdentities = ArrayList<Identity>()
+        var ident = 0
+        var gotOne: Boolean
+        do {
+            gotOne = false
+            val name = storage.getString("$accountUuid.$IDENTITY_NAME_KEY.$ident", null)
+            val email = storage.getString("$accountUuid.$IDENTITY_EMAIL_KEY.$ident", null)
+            val signatureUse = storage.getBoolean("$accountUuid.signatureUse.$ident", false)
+            val signature = storage.getString("$accountUuid.signature.$ident", null)
+            val description = storage.getString("$accountUuid.$IDENTITY_DESCRIPTION_KEY.$ident", null)
+            val replyTo = storage.getString("$accountUuid.replyTo.$ident", null)
+            if (email != null) {
+                val identity = Identity(
+                    name = name,
+                    email = email,
+                    signatureUse = signatureUse,
+                    signature = signature,
+                    description = description,
+                    replyTo = replyTo
+                )
+                newIdentities.add(identity)
+                gotOne = true
+            }
+            ident++
+        } while (gotOne)
+
+        if (newIdentities.isEmpty()) {
+            val name = storage.getString("$accountUuid.name", null)
+            val email = storage.getString("$accountUuid.email", null)
+            val signatureUse = storage.getBoolean("$accountUuid.signatureUse", false)
+            val signature = storage.getString("$accountUuid.signature", null)
+            val identity = Identity(
+                name = name,
+                email = email,
+                signatureUse = signatureUse,
+                signature = signature,
+                description = email
+            )
+            newIdentities.add(identity)
+        }
+
+        return newIdentities
+    }
+
+    @Synchronized
+    fun save(editor: StorageEditor, storage: Storage, account: Account) {
+        val accountUuid = account.uuid
+
+        if (!storage.getString("accountUuids", "").contains(account.uuid)) {
+            var accountUuids = storage.getString("accountUuids", "")
+            accountUuids += (if (accountUuids.isNotEmpty()) "," else "") + account.uuid
+            editor.putString("accountUuids", accountUuids)
+        }
+
+        with(account) {
+            editor.putString("$accountUuid.$INCOMING_SERVER_SETTINGS_KEY", serverSettingsSerializer.serialize(incomingServerSettings))
+            editor.putString("$accountUuid.$OUTGOING_SERVER_SETTINGS_KEY", serverSettingsSerializer.serialize(outgoingServerSettings))
+            editor.putString("$accountUuid.oAuthState", oAuthState)
+            editor.putString("$accountUuid.localStorageProvider", localStorageProviderId)
+            editor.putString("$accountUuid.description", name)
+            editor.putString("$accountUuid.alwaysBcc", alwaysBcc)
+            editor.putInt("$accountUuid.automaticCheckIntervalMinutes", automaticCheckIntervalMinutes)
+            editor.putInt("$accountUuid.idleRefreshMinutes", idleRefreshMinutes)
+            editor.putInt("$accountUuid.displayCount", displayCount)
+            editor.putBoolean("$accountUuid.notifyNewMail", isNotifyNewMail)
+            editor.putString("$accountUuid.folderNotifyNewMailMode", folderNotifyNewMailMode.name)
+            editor.putBoolean("$accountUuid.notifySelfNewMail", isNotifySelfNewMail)
+            editor.putBoolean("$accountUuid.notifyContactsMailOnly", isNotifyContactsMailOnly)
+            editor.putBoolean("$accountUuid.ignoreChatMessages", isIgnoreChatMessages)
+            editor.putBoolean("$accountUuid.notifyMailCheck", isNotifySync)
+            editor.putInt("$accountUuid.messagesNotificationChannelVersion", messagesNotificationChannelVersion)
+            editor.putInt("$accountUuid.deletePolicy", deletePolicy.setting)
+            editor.putString("$accountUuid.inboxFolderName", legacyInboxFolder)
+            editor.putString("$accountUuid.draftsFolderName", importedDraftsFolder)
+            editor.putString("$accountUuid.sentFolderName", importedSentFolder)
+            editor.putString("$accountUuid.trashFolderName", importedTrashFolder)
+            editor.putString("$accountUuid.archiveFolderName", importedArchiveFolder)
+            editor.putString("$accountUuid.spamFolderName", importedSpamFolder)
+            editor.putString("$accountUuid.inboxFolderId", inboxFolderId?.toString())
+            editor.putString("$accountUuid.outboxFolderId", outboxFolderId?.toString())
+            editor.putString("$accountUuid.draftsFolderId", draftsFolderId?.toString())
+            editor.putString("$accountUuid.sentFolderId", sentFolderId?.toString())
+            editor.putString("$accountUuid.trashFolderId", trashFolderId?.toString())
+            editor.putString("$accountUuid.archiveFolderId", archiveFolderId?.toString())
+            editor.putString("$accountUuid.spamFolderId", spamFolderId?.toString())
+            editor.putString("$accountUuid.archiveFolderSelection", archiveFolderSelection.name)
+            editor.putString("$accountUuid.draftsFolderSelection", draftsFolderSelection.name)
+            editor.putString("$accountUuid.sentFolderSelection", sentFolderSelection.name)
+            editor.putString("$accountUuid.spamFolderSelection", spamFolderSelection.name)
+            editor.putString("$accountUuid.trashFolderSelection", trashFolderSelection.name)
+            editor.putString("$accountUuid.autoExpandFolderName", importedAutoExpandFolder)
+            editor.putString("$accountUuid.autoExpandFolderId", autoExpandFolderId?.toString())
+            editor.putInt("$accountUuid.accountNumber", accountNumber)
+            editor.putString("$accountUuid.sortTypeEnum", sortType.name)
+            editor.putBoolean("$accountUuid.sortAscending", isSortAscending(sortType))
+            editor.putString("$accountUuid.showPicturesEnum", showPictures.name)
+            editor.putString("$accountUuid.folderDisplayMode", folderDisplayMode.name)
+            editor.putString("$accountUuid.folderSyncMode", folderSyncMode.name)
+            editor.putString("$accountUuid.folderPushMode", folderPushMode.name)
+            editor.putString("$accountUuid.folderTargetMode", folderTargetMode.name)
+            editor.putBoolean("$accountUuid.signatureBeforeQuotedText", isSignatureBeforeQuotedText)
+            editor.putString("$accountUuid.expungePolicy", expungePolicy.name)
+            editor.putBoolean("$accountUuid.syncRemoteDeletions", isSyncRemoteDeletions)
+            editor.putInt("$accountUuid.maxPushFolders", maxPushFolders)
+            editor.putString("$accountUuid.searchableFolders", searchableFolders.name)
+            editor.putInt("$accountUuid.chipColor", chipColor)
+            editor.putBoolean("$accountUuid.subscribedFoldersOnly", isSubscribedFoldersOnly)
+            editor.putInt("$accountUuid.maximumPolledMessageAge", maximumPolledMessageAge)
+            editor.putInt("$accountUuid.maximumAutoDownloadMessageSize", maximumAutoDownloadMessageSize)
+            val messageFormatAuto = if (MessageFormat.AUTO == messageFormat) {
+                // saving MessageFormat.AUTO as is to the database will cause downgrades to crash on
+                // startup, so we save as MessageFormat.TEXT instead with a separate flag for auto.
+                editor.putString("$accountUuid.messageFormat", MessageFormat.TEXT.name)
+                true
+            } else {
+                editor.putString("$accountUuid.messageFormat", messageFormat.name)
+                false
+            }
+            editor.putBoolean("$accountUuid.messageFormatAuto", messageFormatAuto)
+            editor.putBoolean("$accountUuid.messageReadReceipt", isMessageReadReceipt)
+            editor.putString("$accountUuid.quoteStyle", quoteStyle.name)
+            editor.putString("$accountUuid.quotePrefix", quotePrefix)
+            editor.putBoolean("$accountUuid.defaultQuotedTextShown", isDefaultQuotedTextShown)
+            editor.putBoolean("$accountUuid.replyAfterQuote", isReplyAfterQuote)
+            editor.putBoolean("$accountUuid.stripSignature", isStripSignature)
+            editor.putLong("$accountUuid.cryptoKey", openPgpKey)
+            editor.putBoolean("$accountUuid.openPgpHideSignOnly", isOpenPgpHideSignOnly)
+            editor.putBoolean("$accountUuid.openPgpEncryptSubject", isOpenPgpEncryptSubject)
+            editor.putBoolean("$accountUuid.openPgpEncryptAllDrafts", isOpenPgpEncryptAllDrafts)
+            editor.putString("$accountUuid.openPgpProvider", openPgpProvider)
+            editor.putBoolean("$accountUuid.autocryptMutualMode", autocryptPreferEncryptMutual)
+            editor.putBoolean("$accountUuid.remoteSearchFullText", isRemoteSearchFullText)
+            editor.putInt("$accountUuid.remoteSearchNumResults", remoteSearchNumResults)
+            editor.putBoolean("$accountUuid.uploadSentMessages", isUploadSentMessages)
+            editor.putBoolean("$accountUuid.markMessageAsReadOnView", isMarkMessageAsReadOnView)
+            editor.putBoolean("$accountUuid.markMessageAsReadOnDelete", isMarkMessageAsReadOnDelete)
+            editor.putBoolean("$accountUuid.alwaysShowCcBcc", isAlwaysShowCcBcc)
+
+            editor.putBoolean("$accountUuid.vibrate", notificationSettings.vibration.isEnabled)
+            editor.putInt("$accountUuid.vibratePattern", notificationSettings.vibration.pattern.serialize())
+            editor.putInt("$accountUuid.vibrateTimes", notificationSettings.vibration.repeatCount)
+            editor.putBoolean("$accountUuid.ring", notificationSettings.isRingEnabled)
+            editor.putString("$accountUuid.ringtone", notificationSettings.ringtone)
+            editor.putString("$accountUuid.notificationLight", notificationSettings.light.name)
+            editor.putLong("$accountUuid.lastSyncTime", lastSyncTime)
+            editor.putLong("$accountUuid.lastFolderListRefreshTime", lastFolderListRefreshTime)
+            editor.putBoolean("$accountUuid.isFinishedSetup", isFinishedSetup)
+            editor.putBoolean("$accountUuid.useCompression", useCompression)
+            editor.putBoolean("$accountUuid.migrateToOAuth", shouldMigrateToOAuth)
+        }
+
+        saveIdentities(account, storage, editor)
+    }
+
+    @Synchronized
+    fun delete(editor: StorageEditor, storage: Storage, account: Account) {
+        val accountUuid = account.uuid
+
+        // Get the list of account UUIDs
+        val uuids = storage.getString("accountUuids", "").split(",".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
+
+        // Create a list of all account UUIDs excluding this account
+        val newUuids = ArrayList<String>(uuids.size)
+        for (uuid in uuids) {
+            if (uuid != accountUuid) {
+                newUuids.add(uuid)
+            }
+        }
+
+        // Only change the 'accountUuids' value if this account's UUID was listed before
+        if (newUuids.size < uuids.size) {
+            val accountUuids = Utility.combine(newUuids.toTypedArray(), ',')
+            editor.putString("accountUuids", accountUuids)
+        }
+
+        editor.remove("$accountUuid.$INCOMING_SERVER_SETTINGS_KEY")
+        editor.remove("$accountUuid.$OUTGOING_SERVER_SETTINGS_KEY")
+        editor.remove("$accountUuid.oAuthState")
+        editor.remove("$accountUuid.description")
+        editor.remove("$accountUuid.name")
+        editor.remove("$accountUuid.email")
+        editor.remove("$accountUuid.alwaysBcc")
+        editor.remove("$accountUuid.automaticCheckIntervalMinutes")
+        editor.remove("$accountUuid.idleRefreshMinutes")
+        editor.remove("$accountUuid.lastAutomaticCheckTime")
+        editor.remove("$accountUuid.notifyNewMail")
+        editor.remove("$accountUuid.notifySelfNewMail")
+        editor.remove("$accountUuid.ignoreChatMessages")
+        editor.remove("$accountUuid.messagesNotificationChannelVersion")
+        editor.remove("$accountUuid.deletePolicy")
+        editor.remove("$accountUuid.draftsFolderName")
+        editor.remove("$accountUuid.sentFolderName")
+        editor.remove("$accountUuid.trashFolderName")
+        editor.remove("$accountUuid.archiveFolderName")
+        editor.remove("$accountUuid.spamFolderName")
+        editor.remove("$accountUuid.archiveFolderSelection")
+        editor.remove("$accountUuid.draftsFolderSelection")
+        editor.remove("$accountUuid.sentFolderSelection")
+        editor.remove("$accountUuid.spamFolderSelection")
+        editor.remove("$accountUuid.trashFolderSelection")
+        editor.remove("$accountUuid.autoExpandFolderName")
+        editor.remove("$accountUuid.accountNumber")
+        editor.remove("$accountUuid.vibrate")
+        editor.remove("$accountUuid.vibratePattern")
+        editor.remove("$accountUuid.vibrateTimes")
+        editor.remove("$accountUuid.ring")
+        editor.remove("$accountUuid.ringtone")
+        editor.remove("$accountUuid.folderDisplayMode")
+        editor.remove("$accountUuid.folderSyncMode")
+        editor.remove("$accountUuid.folderPushMode")
+        editor.remove("$accountUuid.folderTargetMode")
+        editor.remove("$accountUuid.signatureBeforeQuotedText")
+        editor.remove("$accountUuid.expungePolicy")
+        editor.remove("$accountUuid.syncRemoteDeletions")
+        editor.remove("$accountUuid.maxPushFolders")
+        editor.remove("$accountUuid.searchableFolders")
+        editor.remove("$accountUuid.chipColor")
+        editor.remove("$accountUuid.notificationLight")
+        editor.remove("$accountUuid.subscribedFoldersOnly")
+        editor.remove("$accountUuid.maximumPolledMessageAge")
+        editor.remove("$accountUuid.maximumAutoDownloadMessageSize")
+        editor.remove("$accountUuid.messageFormatAuto")
+        editor.remove("$accountUuid.quoteStyle")
+        editor.remove("$accountUuid.quotePrefix")
+        editor.remove("$accountUuid.sortTypeEnum")
+        editor.remove("$accountUuid.sortAscending")
+        editor.remove("$accountUuid.showPicturesEnum")
+        editor.remove("$accountUuid.replyAfterQuote")
+        editor.remove("$accountUuid.stripSignature")
+        editor.remove("$accountUuid.cryptoApp") // this is no longer set, but cleans up legacy values
+        editor.remove("$accountUuid.cryptoAutoSignature")
+        editor.remove("$accountUuid.cryptoAutoEncrypt")
+        editor.remove("$accountUuid.cryptoApp")
+        editor.remove("$accountUuid.cryptoKey")
+        editor.remove("$accountUuid.cryptoSupportSignOnly")
+        editor.remove("$accountUuid.openPgpProvider")
+        editor.remove("$accountUuid.openPgpHideSignOnly")
+        editor.remove("$accountUuid.openPgpEncryptSubject")
+        editor.remove("$accountUuid.openPgpEncryptAllDrafts")
+        editor.remove("$accountUuid.autocryptMutualMode")
+        editor.remove("$accountUuid.enabled")
+        editor.remove("$accountUuid.markMessageAsReadOnView")
+        editor.remove("$accountUuid.markMessageAsReadOnDelete")
+        editor.remove("$accountUuid.alwaysShowCcBcc")
+        editor.remove("$accountUuid.remoteSearchFullText")
+        editor.remove("$accountUuid.remoteSearchNumResults")
+        editor.remove("$accountUuid.uploadSentMessages")
+        editor.remove("$accountUuid.defaultQuotedTextShown")
+        editor.remove("$accountUuid.displayCount")
+        editor.remove("$accountUuid.inboxFolderName")
+        editor.remove("$accountUuid.localStorageProvider")
+        editor.remove("$accountUuid.messageFormat")
+        editor.remove("$accountUuid.messageReadReceipt")
+        editor.remove("$accountUuid.notifyMailCheck")
+        editor.remove("$accountUuid.inboxFolderId")
+        editor.remove("$accountUuid.outboxFolderId")
+        editor.remove("$accountUuid.draftsFolderId")
+        editor.remove("$accountUuid.sentFolderId")
+        editor.remove("$accountUuid.trashFolderId")
+        editor.remove("$accountUuid.archiveFolderId")
+        editor.remove("$accountUuid.spamFolderId")
+        editor.remove("$accountUuid.autoExpandFolderId")
+        editor.remove("$accountUuid.lastSyncTime")
+        editor.remove("$accountUuid.lastFolderListRefreshTime")
+        editor.remove("$accountUuid.isFinishedSetup")
+        editor.remove("$accountUuid.useCompression")
+        editor.remove("$accountUuid.migrateToOAuth")
+
+        deleteIdentities(account, storage, editor)
+        // TODO: Remove preference settings that may exist for individual folders in the account.
+    }
+
+    @Synchronized
+    private fun saveIdentities(account: Account, storage: Storage, editor: StorageEditor) {
+        deleteIdentities(account, storage, editor)
+        var ident = 0
+
+        with(account) {
+            for (identity in identities) {
+                editor.putString("$uuid.$IDENTITY_NAME_KEY.$ident", identity.name)
+                editor.putString("$uuid.$IDENTITY_EMAIL_KEY.$ident", identity.email)
+                editor.putBoolean("$uuid.signatureUse.$ident", identity.signatureUse)
+                editor.putString("$uuid.signature.$ident", identity.signature)
+                editor.putString("$uuid.$IDENTITY_DESCRIPTION_KEY.$ident", identity.description)
+                editor.putString("$uuid.replyTo.$ident", identity.replyTo)
+                ident++
+            }
+        }
+    }
+
+    @Synchronized
+    private fun deleteIdentities(account: Account, storage: Storage, editor: StorageEditor) {
+        val accountUuid = account.uuid
+
+        var identityIndex = 0
+        var gotOne: Boolean
+        do {
+            gotOne = false
+            val email = storage.getString("$accountUuid.$IDENTITY_EMAIL_KEY.$identityIndex", null)
+            if (email != null) {
+                editor.remove("$accountUuid.$IDENTITY_NAME_KEY.$identityIndex")
+                editor.remove("$accountUuid.$IDENTITY_EMAIL_KEY.$identityIndex")
+                editor.remove("$accountUuid.signatureUse.$identityIndex")
+                editor.remove("$accountUuid.signature.$identityIndex")
+                editor.remove("$accountUuid.$IDENTITY_DESCRIPTION_KEY.$identityIndex")
+                editor.remove("$accountUuid.replyTo.$identityIndex")
+                gotOne = true
+            }
+            identityIndex++
+        } while (gotOne)
+    }
+
+    fun move(editor: StorageEditor, account: Account, storage: Storage, newPosition: Int) {
+        val accountUuids = storage.getString("accountUuids", "").split(",").filter { it.isNotEmpty() }
+        val oldPosition = accountUuids.indexOf(account.uuid)
+        if (oldPosition == -1 || oldPosition == newPosition) return
+
+        val newAccountUuidsString = accountUuids.toMutableList()
+            .apply {
+                removeAt(oldPosition)
+                add(newPosition, account.uuid)
+            }
+            .joinToString(separator = ",")
+
+        editor.putString("accountUuids", newAccountUuidsString)
+    }
+
+    private fun <T : Enum<T>> getEnumStringPref(storage: Storage, key: String, defaultEnum: T): T {
+        val stringPref = storage.getString(key, null)
+
+        return if (stringPref == null) {
+            defaultEnum
+        } else {
+            try {
+                java.lang.Enum.valueOf<T>(defaultEnum.declaringJavaClass, stringPref)
+            } catch (ex: IllegalArgumentException) {
+                Timber.w(
+                    ex,
+                    "Unable to convert preference key [%s] value [%s] to enum of type %s",
+                    key,
+                    stringPref,
+                    defaultEnum.declaringJavaClass
+                )
+
+                defaultEnum
+            }
+        }
+    }
+
+    fun loadDefaults(account: Account) {
+        with(account) {
+            localStorageProviderId = storageManager.defaultProviderId
+            automaticCheckIntervalMinutes = DEFAULT_SYNC_INTERVAL
+            idleRefreshMinutes = 24
+            displayCount = K9.DEFAULT_VISIBLE_LIMIT
+            accountNumber = UNASSIGNED_ACCOUNT_NUMBER
+            isNotifyNewMail = true
+            folderNotifyNewMailMode = FolderMode.ALL
+            isNotifySync = false
+            isNotifySelfNewMail = true
+            isNotifyContactsMailOnly = false
+            isIgnoreChatMessages = false
+            messagesNotificationChannelVersion = 0
+            folderDisplayMode = FolderMode.NOT_SECOND_CLASS
+            folderSyncMode = FolderMode.FIRST_CLASS
+            folderPushMode = FolderMode.NONE
+            folderTargetMode = FolderMode.NOT_SECOND_CLASS
+            sortType = DEFAULT_SORT_TYPE
+            setSortAscending(DEFAULT_SORT_TYPE, DEFAULT_SORT_ASCENDING)
+            showPictures = ShowPictures.NEVER
+            isSignatureBeforeQuotedText = false
+            expungePolicy = Expunge.EXPUNGE_IMMEDIATELY
+            importedAutoExpandFolder = null
+            legacyInboxFolder = null
+            maxPushFolders = 10
+            isSubscribedFoldersOnly = false
+            maximumPolledMessageAge = -1
+            maximumAutoDownloadMessageSize = 32768
+            messageFormat = DEFAULT_MESSAGE_FORMAT
+            isMessageFormatAuto = DEFAULT_MESSAGE_FORMAT_AUTO
+            isMessageReadReceipt = DEFAULT_MESSAGE_READ_RECEIPT
+            quoteStyle = DEFAULT_QUOTE_STYLE
+            quotePrefix = DEFAULT_QUOTE_PREFIX
+            isDefaultQuotedTextShown = DEFAULT_QUOTED_TEXT_SHOWN
+            isReplyAfterQuote = DEFAULT_REPLY_AFTER_QUOTE
+            isStripSignature = DEFAULT_STRIP_SIGNATURE
+            isSyncRemoteDeletions = true
+            openPgpKey = NO_OPENPGP_KEY
+            isRemoteSearchFullText = false
+            remoteSearchNumResults = DEFAULT_REMOTE_SEARCH_NUM_RESULTS
+            isUploadSentMessages = true
+            isMarkMessageAsReadOnView = true
+            isMarkMessageAsReadOnDelete = true
+            isAlwaysShowCcBcc = false
+            lastSyncTime = 0L
+            lastFolderListRefreshTime = 0L
+
+            setArchiveFolderId(null, SpecialFolderSelection.AUTOMATIC)
+            setDraftsFolderId(null, SpecialFolderSelection.AUTOMATIC)
+            setSentFolderId(null, SpecialFolderSelection.AUTOMATIC)
+            setSpamFolderId(null, SpecialFolderSelection.AUTOMATIC)
+            setTrashFolderId(null, SpecialFolderSelection.AUTOMATIC)
+            setArchiveFolderId(null, SpecialFolderSelection.AUTOMATIC)
+
+            searchableFolders = Searchable.ALL
+
+            identities = ArrayList<Identity>()
+
+            val identity = Identity(
+                signatureUse = false,
+                signature = resourceProvider.defaultSignature(),
+                description = resourceProvider.defaultIdentityDescription()
+            )
+            identities.add(identity)
+
+            updateNotificationSettings {
+                NotificationSettings(
+                    isRingEnabled = true,
+                    ringtone = DEFAULT_RINGTONE_URI,
+                    light = NotificationLight.Disabled,
+                    vibration = NotificationVibration.DEFAULT
+                )
+            }
+
+            resetChangeMarkers()
+        }
+    }
+
+    companion object {
+        const val ACCOUNT_DESCRIPTION_KEY = "description"
+        const val INCOMING_SERVER_SETTINGS_KEY = "incomingServerSettings"
+        const val OUTGOING_SERVER_SETTINGS_KEY = "outgoingServerSettings"
+
+        const val IDENTITY_NAME_KEY = "name"
+        const val IDENTITY_EMAIL_KEY = "email"
+        const val IDENTITY_DESCRIPTION_KEY = "description"
+
+        const val FALLBACK_ACCOUNT_COLOR = 0x0099CC
+
+        @JvmField
+        val DEFAULT_MESSAGE_FORMAT = MessageFormat.HTML
+
+        @JvmField
+        val DEFAULT_QUOTE_STYLE = QuoteStyle.PREFIX
+        const val DEFAULT_MESSAGE_FORMAT_AUTO = false
+        const val DEFAULT_MESSAGE_READ_RECEIPT = false
+        const val DEFAULT_QUOTE_PREFIX = ">"
+        const val DEFAULT_QUOTED_TEXT_SHOWN = true
+        const val DEFAULT_REPLY_AFTER_QUOTE = false
+        const val DEFAULT_STRIP_SIGNATURE = true
+        const val DEFAULT_REMOTE_SEARCH_NUM_RESULTS = 25
+        const val DEFAULT_RINGTONE_URI = "content://settings/system/notification_sound"
+    }
+}

app/core/src/main/java/com/fsck/k9/AccountRemovedListener.kt

@@ -0,0 +1,5 @@
+package com.fsck.k9
+
+fun interface AccountRemovedListener {
+    fun onAccountRemoved(account: Account)
+}

app/core/src/main/java/com/fsck/k9/AccountsChangeListener.java

@@ -0,0 +1,6 @@
+package com.fsck.k9;
+
+
+public interface AccountsChangeListener {
+    void onAccountsChanged();
+}

app/core/src/main/java/com/fsck/k9/ActivityExtensions.kt

@@ -0,0 +1,11 @@
+package com.fsck.k9
+
+import android.app.Activity
+import android.widget.Toast
+import androidx.annotation.StringRes
+
+fun Activity.finishWithErrorToast(@StringRes errorRes: Int, vararg formatArgs: String) {
+    val text = getString(errorRes, *formatArgs)
+    Toast.makeText(this, text, Toast.LENGTH_LONG).show()
+    finish()
+}

app/core/src/main/java/com/fsck/k9/AppConfig.kt

@@ -0,0 +1,5 @@
+package com.fsck.k9
+
+data class AppConfig(
+    val componentsToDisable: List<Class<*>>
+)

app/core/src/main/java/com/fsck/k9/BaseAccount.kt

@@ -0,0 +1,7 @@
+package com.fsck.k9
+
+interface BaseAccount {
+    val uuid: String
+    val name: String?
+    val email: String
+}

app/core/src/main/java/com/fsck/k9/Core.kt

@@ -0,0 +1,89 @@
+package com.fsck.k9
+
+import android.content.ComponentName
+import android.content.Context
+import android.content.pm.PackageManager
+import com.fsck.k9.job.K9JobManager
+import com.fsck.k9.mail.internet.BinaryTempFileBody
+import com.fsck.k9.notification.NotificationController
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import org.koin.core.qualifier.named
+
+object Core : EarlyInit {
+    private val context: Context by inject()
+    private val appConfig: AppConfig by inject()
+    private val jobManager: K9JobManager by inject()
+    private val appCoroutineScope: CoroutineScope by inject(named("AppCoroutineScope"))
+    private val preferences: Preferences by inject()
+    private val notificationController: NotificationController by inject()
+
+    /**
+     * This needs to be called from [Application#onCreate][android.app.Application#onCreate] before calling through
+     * to the super class's `onCreate` implementation and before initializing the dependency injection library.
+     */
+    fun earlyInit() {
+        if (K9.DEVELOPER_MODE) {
+            enableStrictMode()
+        }
+    }
+
+    fun init(context: Context) {
+        BinaryTempFileBody.setTempDirectory(context.cacheDir)
+
+        setServicesEnabled(context)
+
+        restoreNotifications()
+    }
+
+    /**
+     * Called throughout the application when the number of accounts has changed. This method
+     * enables or disables the Compose activity, the boot receiver and the service based on
+     * whether any accounts are configured.
+     */
+    @JvmStatic
+    fun setServicesEnabled(context: Context) {
+        val appContext = context.applicationContext
+        val acctLength = Preferences.getPreferences().accounts.size
+        val enable = acctLength > 0
+
+        setServicesEnabled(appContext, enable)
+    }
+
+    fun setServicesEnabled() {
+        setServicesEnabled(context)
+    }
+
+    private fun setServicesEnabled(context: Context, enabled: Boolean) {
+        val pm = context.packageManager
+
+        for (clazz in appConfig.componentsToDisable) {
+            val alreadyEnabled = pm.getComponentEnabledSetting(ComponentName(context, clazz)) ==
+                PackageManager.COMPONENT_ENABLED_STATE_ENABLED
+
+            if (enabled != alreadyEnabled) {
+                pm.setComponentEnabledSetting(
+                    ComponentName(context, clazz),
+                    if (enabled) {
+                        PackageManager.COMPONENT_ENABLED_STATE_ENABLED
+                    } else {
+                        PackageManager.COMPONENT_ENABLED_STATE_DISABLED
+                    },
+                    PackageManager.DONT_KILL_APP
+                )
+            }
+        }
+
+        if (enabled) {
+            jobManager.scheduleAllMailJobs()
+        }
+    }
+
+    private fun restoreNotifications() {
+        appCoroutineScope.launch(Dispatchers.IO) {
+            val accounts = preferences.accounts
+            notificationController.restoreNewMailNotifications(accounts)
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/CoreKoinModules.kt

@@ -0,0 +1,36 @@
+package com.fsck.k9
+
+import com.fsck.k9.autocrypt.autocryptModule
+import com.fsck.k9.controller.controllerModule
+import com.fsck.k9.controller.push.controllerPushModule
+import com.fsck.k9.crypto.openPgpModule
+import com.fsck.k9.helper.helperModule
+import com.fsck.k9.job.jobModule
+import com.fsck.k9.logging.loggingModule
+import com.fsck.k9.mailstore.mailStoreModule
+import com.fsck.k9.message.extractors.extractorModule
+import com.fsck.k9.message.html.htmlModule
+import com.fsck.k9.message.quote.quoteModule
+import com.fsck.k9.network.connectivityModule
+import com.fsck.k9.notification.coreNotificationModule
+import com.fsck.k9.power.powerModule
+import com.fsck.k9.preferences.preferencesModule
+
+val coreModules = listOf(
+    mainModule,
+    openPgpModule,
+    autocryptModule,
+    mailStoreModule,
+    extractorModule,
+    htmlModule,
+    quoteModule,
+    coreNotificationModule,
+    controllerModule,
+    controllerPushModule,
+    jobModule,
+    helperModule,
+    preferencesModule,
+    connectivityModule,
+    powerModule,
+    loggingModule
+)

app/core/src/main/java/com/fsck/k9/CoreResourceProvider.kt

@@ -0,0 +1,35 @@
+package com.fsck.k9
+
+import com.fsck.k9.notification.PushNotificationState
+
+interface CoreResourceProvider {
+    fun defaultSignature(): String
+    fun defaultIdentityDescription(): String
+
+    fun contactDisplayNamePrefix(): String
+    fun contactUnknownSender(): String
+    fun contactUnknownRecipient(): String
+
+    fun messageHeaderFrom(): String
+    fun messageHeaderTo(): String
+    fun messageHeaderCc(): String
+    fun messageHeaderDate(): String
+    fun messageHeaderSubject(): String
+    fun messageHeaderSeparator(): String
+
+    fun noSubject(): String
+    fun userAgent(): String
+
+    fun encryptedSubject(): String
+    fun replyHeader(sender: String): String
+    fun replyHeader(sender: String, sentDate: String): String
+
+    fun searchUnifiedInboxTitle(): String
+    fun searchUnifiedInboxDetail(): String
+
+    fun outboxFolderName(): String
+
+    val iconPushNotification: Int
+    fun pushNotificationText(notificationState: PushNotificationState): String
+    fun pushNotificationInfoText(): String
+}

app/core/src/main/java/com/fsck/k9/DI.kt

@@ -0,0 +1,44 @@
+package com.fsck.k9
+
+import android.app.Application
+import com.fsck.k9.core.BuildConfig
+import org.koin.android.ext.koin.androidContext
+import org.koin.android.ext.koin.androidLogger
+import org.koin.core.context.startKoin
+import org.koin.core.module.Module
+import org.koin.core.parameter.ParametersDefinition
+import org.koin.core.qualifier.Qualifier
+import org.koin.java.KoinJavaComponent.getKoin
+import org.koin.java.KoinJavaComponent.get as koinGet
+
+object DI {
+    private const val DEBUG = false
+
+    @JvmStatic fun start(application: Application, modules: List<Module>) {
+        startKoin {
+            if (BuildConfig.DEBUG && DEBUG) {
+                androidLogger()
+            }
+
+            androidContext(application)
+            modules(modules)
+        }
+    }
+
+    @JvmStatic
+    fun <T : Any> get(clazz: Class<T>): T {
+        return koinGet(clazz)
+    }
+
+    inline fun <reified T : Any> get(): T {
+        return koinGet(T::class.java)
+    }
+}
+
+interface EarlyInit
+
+// Copied from ComponentCallbacks.inject()
+inline fun <reified T : Any> EarlyInit.inject(
+    qualifier: Qualifier? = null,
+    noinline parameters: ParametersDefinition? = null
+) = lazy { getKoin().get<T>(qualifier, parameters) }

app/core/src/main/java/com/fsck/k9/EmailAddressValidator.kt

@@ -0,0 +1,27 @@
+package com.fsck.k9
+
+import java.util.regex.Pattern
+
+class EmailAddressValidator {
+
+    fun isValidAddressOnly(text: CharSequence): Boolean = EMAIL_ADDRESS_PATTERN.matcher(text).matches()
+
+    companion object {
+
+        // https://www.rfc-editor.org/rfc/rfc2396.txt (3.2.2)
+        // https://www.rfc-editor.org/rfc/rfc5321.txt (4.1.2)
+
+        private const val ALPHA = "[a-zA-Z]"
+        private const val ALPHANUM = "[a-zA-Z0-9]"
+        private const val ATEXT = "[0-9a-zA-Z!#$%&'*+\\-/=?^_`{|}~]"
+        private const val QCONTENT = "([\\p{Graph}\\p{Blank}&&[^\"\\\\]]|\\\\[\\p{Graph}\\p{Blank}])"
+        private const val TOP_LABEL = "(($ALPHA($ALPHANUM|\\-|_)*$ALPHANUM)|$ALPHA)"
+        private const val DOMAIN_LABEL = "(($ALPHANUM($ALPHANUM|\\-|_)*$ALPHANUM)|$ALPHANUM)"
+        private const val HOST_NAME = "((($DOMAIN_LABEL\\.)+$TOP_LABEL)|$DOMAIN_LABEL)"
+
+        private val EMAIL_ADDRESS_PATTERN = Pattern.compile(
+            "^($ATEXT+(\\.$ATEXT+)*|\"$QCONTENT+\")" +
+                "\\@$HOST_NAME"
+        )
+    }
+}

app/core/src/main/java/com/fsck/k9/FontSizes.java

@@ -0,0 +1,197 @@
+package com.fsck.k9;
+
+import android.util.TypedValue;
+import android.widget.TextView;
+
+import com.fsck.k9.preferences.Storage;
+import com.fsck.k9.preferences.StorageEditor;
+
+
+/**
+ * Manage font size of the information displayed in the message list and in the message view.
+ */
+public class FontSizes {
+    private static final String MESSAGE_LIST_SUBJECT = "fontSizeMessageListSubject";
+    private static final String MESSAGE_LIST_SENDER = "fontSizeMessageListSender";
+    private static final String MESSAGE_LIST_DATE = "fontSizeMessageListDate";
+    private static final String MESSAGE_LIST_PREVIEW = "fontSizeMessageListPreview";
+    private static final String MESSAGE_VIEW_ACCOUNT_NAME = "fontSizeMessageViewAccountName";
+    private static final String MESSAGE_VIEW_SENDER = "fontSizeMessageViewSender";
+    private static final String MESSAGE_VIEW_RECIPIENTS = "fontSizeMessageViewTo";
+    private static final String MESSAGE_VIEW_SUBJECT = "fontSizeMessageViewSubject";
+    private static final String MESSAGE_VIEW_DATE = "fontSizeMessageViewDate";
+    private static final String MESSAGE_VIEW_CONTENT_PERCENT = "fontSizeMessageViewContentPercent";
+    private static final String MESSAGE_COMPOSE_INPUT = "fontSizeMessageComposeInput";
+
+    public static final int FONT_DEFAULT = -1;   // Don't force-reset the size of this setting
+    public static final int FONT_10SP = 10;
+    public static final int FONT_12SP = 12;
+    public static final int SMALL = 14;         // ?android:attr/textAppearanceSmall
+    public static final int FONT_16SP = 16;
+    public static final int MEDIUM = 18;        // ?android:attr/textAppearanceMedium
+    public static final int FONT_20SP = 20;
+    public static final int LARGE = 22;         // ?android:attr/textAppearanceLarge
+
+
+    private int messageListSubject;
+    private int messageListSender;
+    private int messageListDate;
+    private int messageListPreview;
+    private int messageViewAccountName;
+    private int messageViewSender;
+    private int messageViewRecipients;
+    private int messageViewSubject;
+    private int messageViewDate;
+    private int messageViewContentPercent;
+    private int messageComposeInput;
+
+
+    public FontSizes() {
+        messageListSubject = FONT_DEFAULT;
+        messageListSender = FONT_DEFAULT;
+        messageListDate = FONT_DEFAULT;
+        messageListPreview = FONT_DEFAULT;
+
+        messageViewAccountName = FONT_DEFAULT;
+        messageViewSender = FONT_DEFAULT;
+        messageViewRecipients = FONT_DEFAULT;
+        messageViewSubject = FONT_DEFAULT;
+        messageViewDate = FONT_DEFAULT;
+        messageViewContentPercent = 100;
+
+        messageComposeInput = MEDIUM;
+    }
+
+    public void save(StorageEditor editor) {
+        editor.putInt(MESSAGE_LIST_SUBJECT, messageListSubject);
+        editor.putInt(MESSAGE_LIST_SENDER, messageListSender);
+        editor.putInt(MESSAGE_LIST_DATE, messageListDate);
+        editor.putInt(MESSAGE_LIST_PREVIEW, messageListPreview);
+
+        editor.putInt(MESSAGE_VIEW_ACCOUNT_NAME, messageViewAccountName);
+        editor.putInt(MESSAGE_VIEW_SENDER, messageViewSender);
+        editor.putInt(MESSAGE_VIEW_RECIPIENTS, messageViewRecipients);
+        editor.putInt(MESSAGE_VIEW_SUBJECT, messageViewSubject);
+        editor.putInt(MESSAGE_VIEW_DATE, messageViewDate);
+        editor.putInt(MESSAGE_VIEW_CONTENT_PERCENT, getMessageViewContentAsPercent());
+
+        editor.putInt(MESSAGE_COMPOSE_INPUT, messageComposeInput);
+    }
+
+    public void load(Storage storage) {
+        messageListSubject = storage.getInt(MESSAGE_LIST_SUBJECT, messageListSubject);
+        messageListSender = storage.getInt(MESSAGE_LIST_SENDER, messageListSender);
+        messageListDate = storage.getInt(MESSAGE_LIST_DATE, messageListDate);
+        messageListPreview = storage.getInt(MESSAGE_LIST_PREVIEW, messageListPreview);
+
+        messageViewAccountName = storage.getInt(MESSAGE_VIEW_ACCOUNT_NAME, messageViewAccountName);
+        messageViewSender = storage.getInt(MESSAGE_VIEW_SENDER, messageViewSender);
+        messageViewRecipients = storage.getInt(MESSAGE_VIEW_RECIPIENTS, messageViewRecipients);
+        messageViewSubject = storage.getInt(MESSAGE_VIEW_SUBJECT, messageViewSubject);
+        messageViewDate = storage.getInt(MESSAGE_VIEW_DATE, messageViewDate);
+
+        loadMessageViewContentPercent(storage);
+
+        messageComposeInput = storage.getInt(MESSAGE_COMPOSE_INPUT, messageComposeInput);
+    }
+
+    private void loadMessageViewContentPercent(Storage storage) {
+        setMessageViewContentAsPercent(storage.getInt(MESSAGE_VIEW_CONTENT_PERCENT, 100));
+    }
+
+    public int getMessageListSubject() {
+        return messageListSubject;
+    }
+
+    public void setMessageListSubject(int messageListSubject) {
+        this.messageListSubject = messageListSubject;
+    }
+
+    public int getMessageListSender() {
+        return messageListSender;
+    }
+
+    public void setMessageListSender(int messageListSender) {
+        this.messageListSender = messageListSender;
+    }
+
+    public int getMessageListDate() {
+        return messageListDate;
+    }
+
+    public void setMessageListDate(int messageListDate) {
+        this.messageListDate = messageListDate;
+    }
+
+    public int getMessageListPreview() {
+        return messageListPreview;
+    }
+
+    public void setMessageListPreview(int messageListPreview) {
+        this.messageListPreview = messageListPreview;
+    }
+
+    public int getMessageViewAccountName() {
+        return messageViewAccountName;
+    }
+
+    public void setMessageViewAccountName(int messageViewAccountName) {
+        this.messageViewAccountName = messageViewAccountName;
+    }
+
+    public int getMessageViewSender() {
+        return messageViewSender;
+    }
+
+    public void setMessageViewSender(int messageViewSender) {
+        this.messageViewSender = messageViewSender;
+    }
+
+    public int getMessageViewRecipients() {
+        return messageViewRecipients;
+    }
+
+    public void setMessageViewRecipients(int messageViewRecipients) {
+        this.messageViewRecipients = messageViewRecipients;
+    }
+
+    public int getMessageViewSubject() {
+        return messageViewSubject;
+    }
+
+    public void setMessageViewSubject(int messageViewSubject) {
+        this.messageViewSubject = messageViewSubject;
+    }
+
+    public int getMessageViewDate() {
+        return messageViewDate;
+    }
+
+    public void setMessageViewDate(int messageViewDate) {
+        this.messageViewDate = messageViewDate;
+    }
+
+    public int getMessageViewContentAsPercent() {
+        return messageViewContentPercent;
+    }
+
+    public void setMessageViewContentAsPercent(int size) {
+        messageViewContentPercent = size;
+    }
+
+    public int getMessageComposeInput() {
+        return messageComposeInput;
+    }
+
+    public void setMessageComposeInput(int messageComposeInput) {
+        this.messageComposeInput = messageComposeInput;
+    }
+
+    // This, arguably, should live somewhere in a view class, but since we call it from activities, fragments
+    // and views, where isn't exactly clear.
+    public void setViewTextSize(TextView v, int fontSize) {
+        if (fontSize != FONT_DEFAULT) {
+            v.setTextSize(TypedValue.COMPLEX_UNIT_SP, fontSize);
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/Identity.kt

@@ -0,0 +1,20 @@
+package com.fsck.k9
+
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
+
+@Parcelize
+data class Identity(
+    val description: String? = null,
+    val name: String? = null,
+    val email: String? = null,
+    val signature: String? = null,
+    val signatureUse: Boolean = false,
+    val replyTo: String? = null
+) : Parcelable {
+    // TODO remove when callers are converted to Kotlin
+    fun withName(name: String?) = copy(name = name)
+    fun withSignature(signature: String?) = copy(signature = signature)
+    fun withSignatureUse(signatureUse: Boolean) = copy(signatureUse = signatureUse)
+    fun withEmail(email: String?) = copy(email = email)
+}

app/core/src/main/java/com/fsck/k9/K9.kt

@@ -0,0 +1,535 @@
+package com.fsck.k9
+
+import android.content.Context
+import android.content.SharedPreferences
+import com.fsck.k9.Account.SortType
+import com.fsck.k9.core.BuildConfig
+import com.fsck.k9.mail.K9MailLib
+import com.fsck.k9.mailstore.LocalStore
+import com.fsck.k9.preferences.RealGeneralSettingsManager
+import com.fsck.k9.preferences.Storage
+import com.fsck.k9.preferences.StorageEditor
+import kotlinx.datetime.Clock
+import timber.log.Timber
+import timber.log.Timber.DebugTree
+
+@Deprecated("Use GeneralSettingsManager and GeneralSettings instead")
+object K9 : EarlyInit {
+    private val generalSettingsManager: RealGeneralSettingsManager by inject()
+
+    /**
+     * If this is `true`, various development settings will be enabled.
+     */
+    @JvmField
+    val DEVELOPER_MODE = BuildConfig.DEBUG
+
+    /**
+     * Name of the [SharedPreferences] file used to store the last known version of the
+     * accounts' databases.
+     *
+     * See `UpgradeDatabases` for a detailed explanation of the database upgrade process.
+     */
+    private const val DATABASE_VERSION_CACHE = "database_version_cache"
+
+    /**
+     * Key used to store the last known database version of the accounts' databases.
+     *
+     * @see DATABASE_VERSION_CACHE
+     */
+    private const val KEY_LAST_ACCOUNT_DATABASE_VERSION = "last_account_database_version"
+
+    /**
+     * A reference to the [SharedPreferences] used for caching the last known database version.
+     *
+     * @see checkCachedDatabaseVersion
+     * @see setDatabasesUpToDate
+     */
+    private var databaseVersionCache: SharedPreferences? = null
+
+    /**
+     * @see areDatabasesUpToDate
+     */
+    private var databasesUpToDate = false
+
+    /**
+     * Check if we already know whether all databases are using the current database schema.
+     *
+     * This method is only used for optimizations. If it returns `true` we can be certain that getting a [LocalStore]
+     * instance won't trigger a schema upgrade.
+     *
+     * @return `true`, if we know that all databases are using the current database schema. `false`, otherwise.
+     */
+    @Synchronized
+    @JvmStatic
+    fun areDatabasesUpToDate(): Boolean {
+        return databasesUpToDate
+    }
+
+    /**
+     * Remember that all account databases are using the most recent database schema.
+     *
+     * @param save
+     * Whether or not to write the current database version to the
+     * `SharedPreferences` [.DATABASE_VERSION_CACHE].
+     *
+     * @see .areDatabasesUpToDate
+     */
+    @Synchronized
+    @JvmStatic
+    fun setDatabasesUpToDate(save: Boolean) {
+        databasesUpToDate = true
+
+        if (save) {
+            val editor = databaseVersionCache!!.edit()
+            editor.putInt(KEY_LAST_ACCOUNT_DATABASE_VERSION, LocalStore.getDbVersion())
+            editor.apply()
+        }
+    }
+
+    /**
+     * Loads the last known database version of the accounts' databases from a `SharedPreference`.
+     *
+     * If the stored version matches [LocalStore.getDbVersion] we know that the databases are up to date.
+     * Using `SharedPreferences` should be a lot faster than opening all SQLite databases to get the current database
+     * version.
+     *
+     * See the class `UpgradeDatabases` for a detailed explanation of the database upgrade process.
+     *
+     * @see areDatabasesUpToDate
+     */
+    private fun checkCachedDatabaseVersion(context: Context) {
+        databaseVersionCache = context.getSharedPreferences(DATABASE_VERSION_CACHE, Context.MODE_PRIVATE)
+
+        val cachedVersion = databaseVersionCache!!.getInt(KEY_LAST_ACCOUNT_DATABASE_VERSION, 0)
+
+        if (cachedVersion >= LocalStore.getDbVersion()) {
+            setDatabasesUpToDate(false)
+        }
+    }
+
+    @JvmStatic
+    var isDebugLoggingEnabled: Boolean = DEVELOPER_MODE
+        set(debug) {
+            field = debug
+            updateLoggingStatus()
+        }
+
+    @JvmStatic
+    var isSensitiveDebugLoggingEnabled: Boolean = false
+
+    @JvmStatic
+    var k9Language = ""
+
+    @JvmStatic
+    val fontSizes = FontSizes()
+
+    @JvmStatic
+    var backgroundOps = BACKGROUND_OPS.ALWAYS
+
+    @JvmStatic
+    var isShowAnimations = true
+
+    @JvmStatic
+    var isConfirmDelete = false
+
+    @JvmStatic
+    var isConfirmDiscardMessage = true
+
+    @JvmStatic
+    var isConfirmDeleteStarred = false
+
+    @JvmStatic
+    var isConfirmSpam = false
+
+    @JvmStatic
+    var isConfirmDeleteFromNotification = true
+
+    @JvmStatic
+    var isConfirmMarkAllRead = true
+
+    @JvmStatic
+    var notificationQuickDeleteBehaviour = NotificationQuickDelete.ALWAYS
+
+    @JvmStatic
+    var lockScreenNotificationVisibility = LockScreenNotificationVisibility.MESSAGE_COUNT
+
+    @JvmStatic
+    var messageListDensity: UiDensity = UiDensity.Default
+
+    @JvmStatic
+    var isShowMessageListStars = true
+
+    @JvmStatic
+    var messageListPreviewLines = 2
+
+    @JvmStatic
+    var isShowCorrespondentNames = true
+
+    @JvmStatic
+    var isMessageListSenderAboveSubject = false
+
+    @JvmStatic
+    var isShowContactName = false
+
+    @JvmStatic
+    var isChangeContactNameColor = false
+
+    @JvmStatic
+    var contactNameColor = 0xFF1093F5.toInt()
+
+    @JvmStatic
+    var isShowContactPicture = true
+
+    @JvmStatic
+    var isUseMessageViewFixedWidthFont = false
+
+    @JvmStatic
+    var isMessageViewReturnToList = false
+
+    @JvmStatic
+    var isMessageViewShowNext = false
+
+    @JvmStatic
+    var isUseVolumeKeysForNavigation = false
+
+    @JvmStatic
+    var isShowUnifiedInbox = true
+
+    @JvmStatic
+    var isShowStarredCount = false
+
+    @JvmStatic
+    var isAutoFitWidth: Boolean = false
+
+    var isQuietTimeEnabled = false
+    var isNotificationDuringQuietTimeEnabled = true
+    var quietTimeStarts: String? = null
+    var quietTimeEnds: String? = null
+
+    @JvmStatic
+    var isHideUserAgent = false
+
+    @JvmStatic
+    var isHideTimeZone = false
+
+    @get:Synchronized
+    @set:Synchronized
+    @JvmStatic
+    var sortType: SortType = Account.DEFAULT_SORT_TYPE
+    private val sortAscending = mutableMapOf<SortType, Boolean>()
+
+    @JvmStatic
+    var isUseBackgroundAsUnreadIndicator = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isShowComposeButtonOnMessageList = true
+
+    @get:Synchronized
+    @set:Synchronized
+    @JvmStatic
+    var isThreadedViewEnabled = true
+
+    @get:Synchronized
+    @set:Synchronized
+    @JvmStatic
+    var splitViewMode = SplitViewMode.NEVER
+
+    var isColorizeMissingContactPictures = true
+
+    @JvmStatic
+    var isMessageViewArchiveActionVisible = false
+
+    @JvmStatic
+    var isMessageViewDeleteActionVisible = true
+
+    @JvmStatic
+    var isMessageViewMoveActionVisible = false
+
+    @JvmStatic
+    var isMessageViewCopyActionVisible = false
+
+    @JvmStatic
+    var isMessageViewSpamActionVisible = false
+
+    @JvmStatic
+    var pgpInlineDialogCounter: Int = 0
+
+    @JvmStatic
+    var pgpSignOnlyDialogCounter: Int = 0
+
+    @JvmStatic
+    var swipeRightAction: SwipeAction = SwipeAction.ToggleSelection
+
+    @JvmStatic
+    var swipeLeftAction: SwipeAction = SwipeAction.ToggleRead
+
+    val isQuietTime: Boolean
+        get() {
+            if (!isQuietTimeEnabled) {
+                return false
+            }
+
+            val clock = DI.get<Clock>()
+            val quietTimeChecker = QuietTimeChecker(clock, quietTimeStarts, quietTimeEnds)
+            return quietTimeChecker.isQuietTime
+        }
+
+    @Synchronized
+    @JvmStatic
+    fun isSortAscending(sortType: SortType): Boolean {
+        if (sortAscending[sortType] == null) {
+            sortAscending[sortType] = sortType.isDefaultAscending
+        }
+        return sortAscending[sortType]!!
+    }
+
+    @Synchronized
+    @JvmStatic
+    fun setSortAscending(sortType: SortType, sortAscending: Boolean) {
+        K9.sortAscending[sortType] = sortAscending
+    }
+
+    fun init(context: Context) {
+        K9MailLib.setDebugStatus(object : K9MailLib.DebugStatus {
+            override fun enabled(): Boolean = isDebugLoggingEnabled
+
+            override fun debugSensitive(): Boolean = isSensitiveDebugLoggingEnabled
+        })
+        com.fsck.k9.logging.Timber.logger = TimberLogger()
+
+        checkCachedDatabaseVersion(context)
+
+        loadPrefs(generalSettingsManager.storage)
+    }
+
+    @JvmStatic
+    fun loadPrefs(storage: Storage) {
+        isDebugLoggingEnabled = storage.getBoolean("enableDebugLogging", DEVELOPER_MODE)
+        isSensitiveDebugLoggingEnabled = storage.getBoolean("enableSensitiveLogging", false)
+        isShowAnimations = storage.getBoolean("animations", true)
+        isUseVolumeKeysForNavigation = storage.getBoolean("useVolumeKeysForNavigation", false)
+        isShowUnifiedInbox = storage.getBoolean("showUnifiedInbox", true)
+        isShowStarredCount = storage.getBoolean("showStarredCount", false)
+        isMessageListSenderAboveSubject = storage.getBoolean("messageListSenderAboveSubject", false)
+        isShowMessageListStars = storage.getBoolean("messageListStars", true)
+        messageListPreviewLines = storage.getInt("messageListPreviewLines", 2)
+
+        isAutoFitWidth = storage.getBoolean("autofitWidth", true)
+
+        isQuietTimeEnabled = storage.getBoolean("quietTimeEnabled", false)
+        isNotificationDuringQuietTimeEnabled = storage.getBoolean("notificationDuringQuietTimeEnabled", true)
+        quietTimeStarts = storage.getString("quietTimeStarts", "21:00")
+        quietTimeEnds = storage.getString("quietTimeEnds", "7:00")
+
+        messageListDensity = storage.getEnum("messageListDensity", UiDensity.Default)
+        isShowCorrespondentNames = storage.getBoolean("showCorrespondentNames", true)
+        isShowContactName = storage.getBoolean("showContactName", false)
+        isShowContactPicture = storage.getBoolean("showContactPicture", true)
+        isChangeContactNameColor = storage.getBoolean("changeRegisteredNameColor", false)
+        contactNameColor = storage.getInt("registeredNameColor", 0xFF1093F5.toInt())
+        isUseMessageViewFixedWidthFont = storage.getBoolean("messageViewFixedWidthFont", false)
+        isMessageViewReturnToList = storage.getBoolean("messageViewReturnToList", false)
+        isMessageViewShowNext = storage.getBoolean("messageViewShowNext", false)
+        isHideUserAgent = storage.getBoolean("hideUserAgent", false)
+        isHideTimeZone = storage.getBoolean("hideTimeZone", false)
+
+        isConfirmDelete = storage.getBoolean("confirmDelete", false)
+        isConfirmDiscardMessage = storage.getBoolean("confirmDiscardMessage", true)
+        isConfirmDeleteStarred = storage.getBoolean("confirmDeleteStarred", false)
+        isConfirmSpam = storage.getBoolean("confirmSpam", false)
+        isConfirmDeleteFromNotification = storage.getBoolean("confirmDeleteFromNotification", true)
+        isConfirmMarkAllRead = storage.getBoolean("confirmMarkAllRead", true)
+
+        sortType = storage.getEnum("sortTypeEnum", Account.DEFAULT_SORT_TYPE)
+
+        val sortAscendingSetting = storage.getBoolean("sortAscending", Account.DEFAULT_SORT_ASCENDING)
+        sortAscending[sortType] = sortAscendingSetting
+
+        notificationQuickDeleteBehaviour = storage.getEnum("notificationQuickDelete", NotificationQuickDelete.ALWAYS)
+
+        lockScreenNotificationVisibility = storage.getEnum(
+            "lockScreenNotificationVisibility",
+            LockScreenNotificationVisibility.MESSAGE_COUNT
+        )
+
+        splitViewMode = storage.getEnum("splitViewMode", SplitViewMode.NEVER)
+
+        isUseBackgroundAsUnreadIndicator = storage.getBoolean("useBackgroundAsUnreadIndicator", false)
+        isShowComposeButtonOnMessageList = storage.getBoolean("showComposeButtonOnMessageList", true)
+        isThreadedViewEnabled = storage.getBoolean("threadedView", true)
+        fontSizes.load(storage)
+
+        backgroundOps = storage.getEnum("backgroundOperations", BACKGROUND_OPS.ALWAYS)
+
+        isColorizeMissingContactPictures = storage.getBoolean("colorizeMissingContactPictures", true)
+
+        isMessageViewArchiveActionVisible = storage.getBoolean("messageViewArchiveActionVisible", false)
+        isMessageViewDeleteActionVisible = storage.getBoolean("messageViewDeleteActionVisible", true)
+        isMessageViewMoveActionVisible = storage.getBoolean("messageViewMoveActionVisible", false)
+        isMessageViewCopyActionVisible = storage.getBoolean("messageViewCopyActionVisible", false)
+        isMessageViewSpamActionVisible = storage.getBoolean("messageViewSpamActionVisible", false)
+
+        pgpInlineDialogCounter = storage.getInt("pgpInlineDialogCounter", 0)
+        pgpSignOnlyDialogCounter = storage.getInt("pgpSignOnlyDialogCounter", 0)
+
+        k9Language = storage.getString("language", "")
+
+        swipeRightAction = storage.getEnum("swipeRightAction", SwipeAction.ToggleSelection)
+        swipeLeftAction = storage.getEnum("swipeLeftAction", SwipeAction.ToggleRead)
+    }
+
+    internal fun save(editor: StorageEditor) {
+        editor.putBoolean("enableDebugLogging", isDebugLoggingEnabled)
+        editor.putBoolean("enableSensitiveLogging", isSensitiveDebugLoggingEnabled)
+        editor.putEnum("backgroundOperations", backgroundOps)
+        editor.putBoolean("animations", isShowAnimations)
+        editor.putBoolean("useVolumeKeysForNavigation", isUseVolumeKeysForNavigation)
+        editor.putBoolean("autofitWidth", isAutoFitWidth)
+        editor.putBoolean("quietTimeEnabled", isQuietTimeEnabled)
+        editor.putBoolean("notificationDuringQuietTimeEnabled", isNotificationDuringQuietTimeEnabled)
+        editor.putString("quietTimeStarts", quietTimeStarts)
+        editor.putString("quietTimeEnds", quietTimeEnds)
+
+        editor.putEnum("messageListDensity", messageListDensity)
+        editor.putBoolean("messageListSenderAboveSubject", isMessageListSenderAboveSubject)
+        editor.putBoolean("showUnifiedInbox", isShowUnifiedInbox)
+        editor.putBoolean("showStarredCount", isShowStarredCount)
+        editor.putBoolean("messageListStars", isShowMessageListStars)
+        editor.putInt("messageListPreviewLines", messageListPreviewLines)
+        editor.putBoolean("showCorrespondentNames", isShowCorrespondentNames)
+        editor.putBoolean("showContactName", isShowContactName)
+        editor.putBoolean("showContactPicture", isShowContactPicture)
+        editor.putBoolean("changeRegisteredNameColor", isChangeContactNameColor)
+        editor.putInt("registeredNameColor", contactNameColor)
+        editor.putBoolean("messageViewFixedWidthFont", isUseMessageViewFixedWidthFont)
+        editor.putBoolean("messageViewReturnToList", isMessageViewReturnToList)
+        editor.putBoolean("messageViewShowNext", isMessageViewShowNext)
+        editor.putBoolean("hideUserAgent", isHideUserAgent)
+        editor.putBoolean("hideTimeZone", isHideTimeZone)
+
+        editor.putString("language", k9Language)
+
+        editor.putBoolean("confirmDelete", isConfirmDelete)
+        editor.putBoolean("confirmDiscardMessage", isConfirmDiscardMessage)
+        editor.putBoolean("confirmDeleteStarred", isConfirmDeleteStarred)
+        editor.putBoolean("confirmSpam", isConfirmSpam)
+        editor.putBoolean("confirmDeleteFromNotification", isConfirmDeleteFromNotification)
+        editor.putBoolean("confirmMarkAllRead", isConfirmMarkAllRead)
+
+        editor.putEnum("sortTypeEnum", sortType)
+        editor.putBoolean("sortAscending", sortAscending[sortType] ?: false)
+
+        editor.putString("notificationQuickDelete", notificationQuickDeleteBehaviour.toString())
+        editor.putString("lockScreenNotificationVisibility", lockScreenNotificationVisibility.toString())
+
+        editor.putBoolean("useBackgroundAsUnreadIndicator", isUseBackgroundAsUnreadIndicator)
+        editor.putBoolean("showComposeButtonOnMessageList", isShowComposeButtonOnMessageList)
+        editor.putBoolean("threadedView", isThreadedViewEnabled)
+        editor.putEnum("splitViewMode", splitViewMode)
+        editor.putBoolean("colorizeMissingContactPictures", isColorizeMissingContactPictures)
+
+        editor.putBoolean("messageViewArchiveActionVisible", isMessageViewArchiveActionVisible)
+        editor.putBoolean("messageViewDeleteActionVisible", isMessageViewDeleteActionVisible)
+        editor.putBoolean("messageViewMoveActionVisible", isMessageViewMoveActionVisible)
+        editor.putBoolean("messageViewCopyActionVisible", isMessageViewCopyActionVisible)
+        editor.putBoolean("messageViewSpamActionVisible", isMessageViewSpamActionVisible)
+
+        editor.putInt("pgpInlineDialogCounter", pgpInlineDialogCounter)
+        editor.putInt("pgpSignOnlyDialogCounter", pgpSignOnlyDialogCounter)
+
+        editor.putEnum("swipeRightAction", swipeRightAction)
+        editor.putEnum("swipeLeftAction", swipeLeftAction)
+
+        fontSizes.save(editor)
+    }
+
+    private fun updateLoggingStatus() {
+        Timber.uprootAll()
+        if (isDebugLoggingEnabled) {
+            Timber.plant(DebugTree())
+        }
+    }
+
+    @JvmStatic
+    fun saveSettingsAsync() {
+        generalSettingsManager.saveSettingsAsync()
+    }
+
+    private inline fun <reified T : Enum<T>> Storage.getEnum(key: String, defaultValue: T): T {
+        return try {
+            val value = getString(key, null)
+            if (value != null) {
+                enumValueOf(value)
+            } else {
+                defaultValue
+            }
+        } catch (e: Exception) {
+            Timber.e("Couldn't read setting '%s'. Using default value instead.", key)
+            defaultValue
+        }
+    }
+
+    private fun <T : Enum<T>> StorageEditor.putEnum(key: String, value: T) {
+        putString(key, value.name)
+    }
+
+    const val LOCAL_UID_PREFIX = "K9LOCAL:"
+
+    const val IDENTITY_HEADER = K9MailLib.IDENTITY_HEADER
+
+    /**
+     * Specifies how many messages will be shown in a folder by default. This number is set
+     * on each new folder and can be incremented with "Load more messages..." by the
+     * VISIBLE_LIMIT_INCREMENT
+     */
+    const val DEFAULT_VISIBLE_LIMIT = 25
+
+    /**
+     * The maximum size of an attachment we're willing to download (either View or Save)
+     * Attachments that are base64 encoded (most) will be about 1.375x their actual size
+     * so we should probably factor that in. A 5MB attachment will generally be around
+     * 6.8MB downloaded but only 5MB saved.
+     */
+    const val MAX_ATTACHMENT_DOWNLOAD_SIZE = 128 * 1024 * 1024
+
+    /**
+     * How many times should K-9 try to deliver a message before giving up until the app is killed and restarted
+     */
+    const val MAX_SEND_ATTEMPTS = 5
+
+    const val MANUAL_WAKE_LOCK_TIMEOUT = 120000
+    const val PUSH_WAKE_LOCK_TIMEOUT = K9MailLib.PUSH_WAKE_LOCK_TIMEOUT
+    const val MAIL_SERVICE_WAKE_LOCK_TIMEOUT = 60000
+    const val BOOT_RECEIVER_WAKE_LOCK_TIMEOUT = 60000
+
+    enum class BACKGROUND_OPS {
+        ALWAYS, NEVER, WHEN_CHECKED_AUTO_SYNC
+    }
+
+    /**
+     * Controls behaviour of delete button in notifications.
+     */
+    enum class NotificationQuickDelete {
+        ALWAYS,
+        FOR_SINGLE_MSG,
+        NEVER
+    }
+
+    enum class LockScreenNotificationVisibility {
+        EVERYTHING,
+        SENDERS,
+        MESSAGE_COUNT,
+        APP_NAME,
+        NOTHING
+    }
+
+    /**
+     * Controls when to use the message list split view.
+     */
+    enum class SplitViewMode {
+        ALWAYS,
+        NEVER,
+        WHEN_IN_LANDSCAPE
+    }
+}

app/core/src/main/java/com/fsck/k9/KoinModule.kt

@@ -0,0 +1,40 @@
+package com.fsck.k9
+
+import android.content.Context
+import app.k9mail.core.android.common.coreCommonAndroidModule
+import com.fsck.k9.helper.Contacts
+import com.fsck.k9.helper.DefaultTrustedSocketFactory
+import com.fsck.k9.mail.ssl.LocalKeyStore
+import com.fsck.k9.mail.ssl.TrustManagerFactory
+import com.fsck.k9.mail.ssl.TrustedSocketFactory
+import com.fsck.k9.mailstore.LocalStoreProvider
+import com.fsck.k9.setup.ServerNameSuggester
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.GlobalScope
+import kotlinx.datetime.Clock
+import org.koin.core.qualifier.named
+import org.koin.dsl.module
+
+val mainModule = module {
+    includes(coreCommonAndroidModule)
+    single<CoroutineScope>(named("AppCoroutineScope")) { GlobalScope }
+    single {
+        Preferences(
+            storagePersister = get(),
+            localStoreProvider = get(),
+            accountPreferenceSerializer = get()
+        )
+    }
+    single { get<Context>().resources }
+    single { get<Context>().contentResolver }
+    single { LocalStoreProvider() }
+    single { Contacts() }
+    single { LocalKeyStore(directoryProvider = get()) }
+    single { TrustManagerFactory.createInstance(get()) }
+    single { LocalKeyStoreManager(get()) }
+    single<TrustedSocketFactory> { DefaultTrustedSocketFactory(get(), get()) }
+    single<Clock> { Clock.System }
+    factory { ServerNameSuggester() }
+    factory { EmailAddressValidator() }
+    factory { ServerSettingsSerializer() }
+}

app/core/src/main/java/com/fsck/k9/LocalKeyStoreManager.kt

@@ -0,0 +1,59 @@
+package com.fsck.k9
+
+import com.fsck.k9.mail.MailServerDirection
+import com.fsck.k9.mail.ssl.LocalKeyStore
+import java.security.cert.CertificateException
+import java.security.cert.X509Certificate
+
+class LocalKeyStoreManager(
+    private val localKeyStore: LocalKeyStore
+) {
+    /**
+     * Add a new certificate for the incoming or outgoing server to the local key store.
+     */
+    @Throws(CertificateException::class)
+    fun addCertificate(account: Account, direction: MailServerDirection, certificate: X509Certificate) {
+        val serverSettings = if (direction === MailServerDirection.INCOMING) {
+            account.incomingServerSettings
+        } else {
+            account.outgoingServerSettings
+        }
+        localKeyStore.addCertificate(serverSettings.host!!, serverSettings.port, certificate)
+    }
+
+    /**
+     * Examine the existing settings for an account.  If the old host/port is different from the
+     * new host/port, then try and delete any (possibly non-existent) certificate stored for the
+     * old host/port.
+     */
+    fun deleteCertificate(account: Account, newHost: String, newPort: Int, direction: MailServerDirection) {
+        val serverSettings = if (direction === MailServerDirection.INCOMING) {
+            account.incomingServerSettings
+        } else {
+            account.outgoingServerSettings
+        }
+        val oldHost = serverSettings.host!!
+        val oldPort = serverSettings.port
+        if (oldPort == -1) {
+            // This occurs when a new account is created
+            return
+        }
+        if (newHost != oldHost || newPort != oldPort) {
+            localKeyStore.deleteCertificate(oldHost, oldPort)
+        }
+    }
+
+    /**
+     * Examine the settings for the account and attempt to delete (possibly non-existent)
+     * certificates for the incoming and outgoing servers.
+     */
+    fun deleteCertificates(account: Account) {
+        account.incomingServerSettings.let { serverSettings ->
+            localKeyStore.deleteCertificate(serverSettings.host!!, serverSettings.port)
+        }
+
+        account.outgoingServerSettings.let { serverSettings ->
+            localKeyStore.deleteCertificate(serverSettings.host!!, serverSettings.port)
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/NotificationLight.kt

@@ -0,0 +1,33 @@
+package com.fsck.k9
+
+import android.app.Notification
+
+enum class NotificationLight {
+    Disabled,
+    AccountColor,
+    SystemDefaultColor,
+    White,
+    Red,
+    Green,
+    Blue,
+    Yellow,
+    Cyan,
+    Magenta;
+
+    fun toColor(account: Account): Int? {
+        return when (this) {
+            Disabled -> null
+            AccountColor -> account.chipColor.toArgb()
+            SystemDefaultColor -> Notification.COLOR_DEFAULT
+            White -> 0xFFFFFF.toArgb()
+            Red -> 0xFF0000.toArgb()
+            Green -> 0x00FF00.toArgb()
+            Blue -> 0x0000FF.toArgb()
+            Yellow -> 0xFFFF00.toArgb()
+            Cyan -> 0x00FFFF.toArgb()
+            Magenta -> 0xFF00FF.toArgb()
+        }
+    }
+
+    private fun Int.toArgb() = this or 0xFF000000L.toInt()
+}

app/core/src/main/java/com/fsck/k9/NotificationSettings.kt

@@ -0,0 +1,11 @@
+package com.fsck.k9
+
+/**
+ * Describes how a notification should behave.
+ */
+data class NotificationSettings(
+    val isRingEnabled: Boolean = false,
+    val ringtone: String? = null,
+    val light: NotificationLight = NotificationLight.Disabled,
+    val vibration: NotificationVibration = NotificationVibration.DEFAULT
+)

app/core/src/main/java/com/fsck/k9/NotificationVibration.kt

@@ -0,0 +1,62 @@
+package com.fsck.k9
+
+data class NotificationVibration(
+    val isEnabled: Boolean,
+    val pattern: VibratePattern,
+    val repeatCount: Int
+) {
+    val systemPattern: LongArray
+        get() = getSystemPattern(pattern, repeatCount)
+
+    companion object {
+        val DEFAULT = NotificationVibration(isEnabled = false, pattern = VibratePattern.Default, repeatCount = 5)
+
+        fun getSystemPattern(vibratePattern: VibratePattern, repeatCount: Int): LongArray {
+            val selectedPattern = vibratePattern.vibrationPattern
+            val repeatedPattern = LongArray(selectedPattern.size * repeatCount)
+            for (n in 0 until repeatCount) {
+                System.arraycopy(selectedPattern, 0, repeatedPattern, n * selectedPattern.size, selectedPattern.size)
+            }
+
+            // Do not wait before starting the vibration pattern.
+            repeatedPattern[0] = 0
+
+            return repeatedPattern
+        }
+    }
+}
+
+enum class VibratePattern(
+    /**
+     * These are "off, on" patterns, specified in milliseconds.
+     */
+    val vibrationPattern: LongArray
+) {
+    Default(vibrationPattern = longArrayOf(300, 200)),
+    Pattern1(vibrationPattern = longArrayOf(100, 200)),
+    Pattern2(vibrationPattern = longArrayOf(100, 500)),
+    Pattern3(vibrationPattern = longArrayOf(200, 200)),
+    Pattern4(vibrationPattern = longArrayOf(200, 500)),
+    Pattern5(vibrationPattern = longArrayOf(500, 500));
+
+    fun serialize(): Int = when (this) {
+        Default -> 0
+        Pattern1 -> 1
+        Pattern2 -> 2
+        Pattern3 -> 3
+        Pattern4 -> 4
+        Pattern5 -> 5
+    }
+
+    companion object {
+        fun deserialize(value: Int): VibratePattern = when (value) {
+            0 -> Default
+            1 -> Pattern1
+            2 -> Pattern2
+            3 -> Pattern3
+            4 -> Pattern4
+            5 -> Pattern5
+            else -> error("Unknown VibratePattern value: $value")
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/Preferences.kt

@@ -0,0 +1,300 @@
+package com.fsck.k9
+
+import androidx.annotation.GuardedBy
+import androidx.annotation.RestrictTo
+import com.fsck.k9.mail.MessagingException
+import com.fsck.k9.mailstore.LocalStoreProvider
+import com.fsck.k9.preferences.AccountManager
+import com.fsck.k9.preferences.Storage
+import com.fsck.k9.preferences.StorageEditor
+import com.fsck.k9.preferences.StoragePersister
+import java.util.HashMap
+import java.util.LinkedList
+import java.util.UUID
+import java.util.concurrent.CopyOnWriteArraySet
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.channels.trySendBlocking
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.buffer
+import kotlinx.coroutines.flow.callbackFlow
+import kotlinx.coroutines.flow.flowOn
+import timber.log.Timber
+
+class Preferences internal constructor(
+    private val storagePersister: StoragePersister,
+    private val localStoreProvider: LocalStoreProvider,
+    private val accountPreferenceSerializer: AccountPreferenceSerializer,
+    private val backgroundDispatcher: CoroutineDispatcher = Dispatchers.IO
+) : AccountManager {
+    private val accountLock = Any()
+    private val storageLock = Any()
+
+    @GuardedBy("accountLock")
+    private var accountsMap: MutableMap<String, Account>? = null
+
+    @GuardedBy("accountLock")
+    private var accountsInOrder = mutableListOf<Account>()
+
+    @GuardedBy("accountLock")
+    private var newAccount: Account? = null
+    private val accountsChangeListeners = CopyOnWriteArraySet<AccountsChangeListener>()
+    private val accountRemovedListeners = CopyOnWriteArraySet<AccountRemovedListener>()
+
+    @GuardedBy("storageLock")
+    private var currentStorage: Storage? = null
+
+    val storage: Storage
+        get() = synchronized(storageLock) {
+            currentStorage ?: storagePersister.loadValues().also { newStorage ->
+                currentStorage = newStorage
+            }
+        }
+
+    fun createStorageEditor(): StorageEditor {
+        return storagePersister.createStorageEditor { updater ->
+            synchronized(storageLock) {
+                currentStorage = updater(storage)
+            }
+        }
+    }
+
+    @RestrictTo(RestrictTo.Scope.TESTS)
+    fun clearAccounts() {
+        synchronized(accountLock) {
+            accountsMap = HashMap()
+            accountsInOrder = LinkedList()
+        }
+    }
+
+    fun loadAccounts() {
+        synchronized(accountLock) {
+            val accounts = mutableMapOf<String, Account>()
+            val accountsInOrder = mutableListOf<Account>()
+
+            val accountUuids = storage.getString("accountUuids", null)
+            if (!accountUuids.isNullOrEmpty()) {
+                accountUuids.split(",").forEach { uuid ->
+                    val newAccount = Account(uuid)
+                    accountPreferenceSerializer.loadAccount(newAccount, storage)
+
+                    accounts[uuid] = newAccount
+                    accountsInOrder.add(newAccount)
+                }
+            }
+
+            newAccount?.takeIf { it.accountNumber != -1 }?.let { newAccount ->
+                accounts[newAccount.uuid] = newAccount
+                if (newAccount !in accountsInOrder) {
+                    accountsInOrder.add(newAccount)
+                }
+                this.newAccount = null
+            }
+
+            this.accountsMap = accounts
+            this.accountsInOrder = accountsInOrder
+        }
+    }
+
+    val accounts: List<Account>
+        get() {
+            synchronized(accountLock) {
+                if (accountsMap == null) {
+                    loadAccounts()
+                }
+
+                return accountsInOrder.toList()
+            }
+        }
+
+    private val completeAccounts: List<Account>
+        get() = accounts.filter { it.isFinishedSetup }
+
+    override fun getAccount(accountUuid: String): Account? {
+        synchronized(accountLock) {
+            if (accountsMap == null) {
+                loadAccounts()
+            }
+
+            return accountsMap!![accountUuid]
+        }
+    }
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    override fun getAccountFlow(accountUuid: String): Flow<Account> {
+        return callbackFlow {
+            val initialAccount = getAccount(accountUuid)
+            if (initialAccount == null) {
+                close()
+                return@callbackFlow
+            }
+
+            send(initialAccount)
+
+            val listener = AccountsChangeListener {
+                val account = getAccount(accountUuid)
+                if (account != null) {
+                    trySendBlocking(account)
+                } else {
+                    close()
+                }
+            }
+            addOnAccountsChangeListener(listener)
+
+            awaitClose {
+                removeOnAccountsChangeListener(listener)
+            }
+        }.buffer(capacity = Channel.CONFLATED)
+            .flowOn(backgroundDispatcher)
+    }
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    override fun getAccountsFlow(): Flow<List<Account>> {
+        return callbackFlow {
+            send(completeAccounts)
+
+            val listener = AccountsChangeListener {
+                trySendBlocking(completeAccounts)
+            }
+            addOnAccountsChangeListener(listener)
+
+            awaitClose {
+                removeOnAccountsChangeListener(listener)
+            }
+        }.buffer(capacity = Channel.CONFLATED)
+            .flowOn(backgroundDispatcher)
+    }
+
+    fun newAccount(): Account {
+        val accountUuid = UUID.randomUUID().toString()
+        val account = Account(accountUuid)
+        accountPreferenceSerializer.loadDefaults(account)
+
+        synchronized(accountLock) {
+            newAccount = account
+            accountsMap!![account.uuid] = account
+            accountsInOrder.add(account)
+        }
+
+        return account
+    }
+
+    fun deleteAccount(account: Account) {
+        synchronized(accountLock) {
+            accountsMap?.remove(account.uuid)
+            accountsInOrder.remove(account)
+
+            val storageEditor = createStorageEditor()
+            accountPreferenceSerializer.delete(storageEditor, storage, account)
+            storageEditor.commit()
+
+            if (account === newAccount) {
+                newAccount = null
+            }
+        }
+
+        notifyAccountRemovedListeners(account)
+        notifyAccountsChangeListeners()
+    }
+
+    val defaultAccount: Account?
+        get() = accounts.firstOrNull()
+
+    override fun saveAccount(account: Account) {
+        ensureAssignedAccountNumber(account)
+        processChangedValues(account)
+
+        synchronized(accountLock) {
+            val editor = createStorageEditor()
+            accountPreferenceSerializer.save(editor, storage, account)
+            editor.commit()
+        }
+
+        notifyAccountsChangeListeners()
+    }
+
+    private fun ensureAssignedAccountNumber(account: Account) {
+        if (account.accountNumber != Account.UNASSIGNED_ACCOUNT_NUMBER) return
+
+        account.accountNumber = generateAccountNumber()
+    }
+
+    private fun processChangedValues(account: Account) {
+        if (account.isChangedVisibleLimits) {
+            try {
+                localStoreProvider.getInstance(account).resetVisibleLimits(account.displayCount)
+            } catch (e: MessagingException) {
+                Timber.e(e, "Failed to load LocalStore!")
+            }
+        }
+        account.resetChangeMarkers()
+    }
+
+    fun generateAccountNumber(): Int {
+        val accountNumbers = accounts.map { it.accountNumber }
+        return findNewAccountNumber(accountNumbers)
+    }
+
+    private fun findNewAccountNumber(accountNumbers: List<Int>): Int {
+        var newAccountNumber = -1
+        for (accountNumber in accountNumbers.sorted()) {
+            if (accountNumber > newAccountNumber + 1) {
+                break
+            }
+            newAccountNumber = accountNumber
+        }
+        newAccountNumber++
+
+        return newAccountNumber
+    }
+
+    override fun moveAccount(account: Account, newPosition: Int) {
+        synchronized(accountLock) {
+            val storageEditor = createStorageEditor()
+            accountPreferenceSerializer.move(storageEditor, account, storage, newPosition)
+            storageEditor.commit()
+
+            loadAccounts()
+        }
+
+        notifyAccountsChangeListeners()
+    }
+
+    private fun notifyAccountsChangeListeners() {
+        for (listener in accountsChangeListeners) {
+            listener.onAccountsChanged()
+        }
+    }
+
+    override fun addOnAccountsChangeListener(accountsChangeListener: AccountsChangeListener) {
+        accountsChangeListeners.add(accountsChangeListener)
+    }
+
+    override fun removeOnAccountsChangeListener(accountsChangeListener: AccountsChangeListener) {
+        accountsChangeListeners.remove(accountsChangeListener)
+    }
+
+    private fun notifyAccountRemovedListeners(account: Account) {
+        for (listener in accountRemovedListeners) {
+            listener.onAccountRemoved(account)
+        }
+    }
+
+    override fun addAccountRemovedListener(listener: AccountRemovedListener) {
+        accountRemovedListeners.add(listener)
+    }
+
+    fun removeAccountRemovedListener(listener: AccountRemovedListener) {
+        accountRemovedListeners.remove(listener)
+    }
+
+    companion object {
+        @JvmStatic
+        fun getPreferences(): Preferences {
+            return DI.get()
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/QuietTimeChecker.java

@@ -0,0 +1,46 @@
+package com.fsck.k9;
+
+
+import java.util.Calendar;
+
+import kotlinx.datetime.Clock;
+
+
+class QuietTimeChecker {
+    private final Clock clock;
+    private final int quietTimeStart;
+    private final int quietTimeEnd;
+
+
+    QuietTimeChecker(Clock clock, String quietTimeStart, String quietTimeEnd) {
+        this.clock = clock;
+        this.quietTimeStart = parseTime(quietTimeStart);
+        this.quietTimeEnd = parseTime(quietTimeEnd);
+    }
+
+    private static int parseTime(String time) {
+        String[] parts = time.split(":");
+        int hour = Integer.parseInt(parts[0]);
+        int minute = Integer.parseInt(parts[1]);
+
+        return hour * 60 + minute;
+    }
+
+    public boolean isQuietTime() {
+        // If start and end times are the same, we're never quiet
+        if (quietTimeStart == quietTimeEnd) {
+            return false;
+        }
+
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTimeInMillis(clock.now().toEpochMilliseconds());
+
+        int minutesSinceMidnight = (calendar.get(Calendar.HOUR_OF_DAY) * 60) + calendar.get(Calendar.MINUTE);
+
+        if (quietTimeStart > quietTimeEnd) {
+            return minutesSinceMidnight >= quietTimeStart || minutesSinceMidnight <= quietTimeEnd;
+        } else {
+            return minutesSinceMidnight >= quietTimeStart && minutesSinceMidnight <= quietTimeEnd;
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/ServerSettingsSerializer.kt

@@ -0,0 +1,122 @@
+package com.fsck.k9
+
+import com.fsck.k9.mail.AuthType
+import com.fsck.k9.mail.ConnectionSecurity
+import com.fsck.k9.mail.ServerSettings
+import com.squareup.moshi.JsonAdapter
+import com.squareup.moshi.JsonReader
+import com.squareup.moshi.JsonReader.Token
+import com.squareup.moshi.JsonWriter
+
+class ServerSettingsSerializer {
+    private val adapter = ServerSettingsAdapter()
+
+    fun serialize(serverSettings: ServerSettings): String {
+        return adapter.toJson(serverSettings)
+    }
+
+    fun deserialize(json: String): ServerSettings {
+        return adapter.fromJson(json)!!
+    }
+}
+
+private const val KEY_TYPE = "type"
+private const val KEY_HOST = "host"
+private const val KEY_PORT = "port"
+private const val KEY_CONNECTION_SECURITY = "connectionSecurity"
+private const val KEY_AUTHENTICATION_TYPE = "authenticationType"
+private const val KEY_USERNAME = "username"
+private const val KEY_PASSWORD = "password"
+private const val KEY_CLIENT_CERTIFICATE_ALIAS = "clientCertificateAlias"
+
+private val JSON_KEYS = JsonReader.Options.of(
+    KEY_TYPE,
+    KEY_HOST,
+    KEY_PORT,
+    KEY_CONNECTION_SECURITY,
+    KEY_AUTHENTICATION_TYPE,
+    KEY_USERNAME,
+    KEY_PASSWORD,
+    KEY_CLIENT_CERTIFICATE_ALIAS
+)
+
+private class ServerSettingsAdapter : JsonAdapter<ServerSettings>() {
+    override fun fromJson(reader: JsonReader): ServerSettings {
+        reader.beginObject()
+
+        var type: String? = null
+        var host: String? = null
+        var port: Int? = null
+        var connectionSecurity: ConnectionSecurity? = null
+        var authenticationType: AuthType? = null
+        var username: String? = null
+        var password: String? = null
+        var clientCertificateAlias: String? = null
+        val extra = mutableMapOf<String, String?>()
+
+        while (reader.hasNext()) {
+            when (reader.selectName(JSON_KEYS)) {
+                0 -> type = reader.nextString()
+                1 -> host = reader.nextString()
+                2 -> port = reader.nextInt()
+                3 -> connectionSecurity = ConnectionSecurity.valueOf(reader.nextString())
+                4 -> authenticationType = AuthType.valueOf(reader.nextString())
+                5 -> username = reader.nextString()
+                6 -> password = reader.nextStringOrNull()
+                7 -> clientCertificateAlias = reader.nextStringOrNull()
+                else -> {
+                    val key = reader.nextName()
+                    val value = reader.nextStringOrNull()
+                    extra[key] = value
+                }
+            }
+        }
+
+        reader.endObject()
+
+        requireNotNull(type) { "'type' must not be missing" }
+        requireNotNull(host) { "'host' must not be missing" }
+        requireNotNull(port) { "'port' must not be missing" }
+        requireNotNull(connectionSecurity) { "'connectionSecurity' must not be missing" }
+        requireNotNull(authenticationType) { "'authenticationType' must not be missing" }
+        requireNotNull(username) { "'username' must not be missing" }
+
+        return ServerSettings(
+            type,
+            host,
+            port,
+            connectionSecurity,
+            authenticationType,
+            username,
+            password,
+            clientCertificateAlias,
+            extra
+        )
+    }
+
+    override fun toJson(writer: JsonWriter, serverSettings: ServerSettings?) {
+        requireNotNull(serverSettings)
+
+        writer.beginObject()
+        writer.serializeNulls = true
+
+        writer.name(KEY_TYPE).value(serverSettings.type)
+        writer.name(KEY_HOST).value(serverSettings.host)
+        writer.name(KEY_PORT).value(serverSettings.port)
+        writer.name(KEY_CONNECTION_SECURITY).value(serverSettings.connectionSecurity.name)
+        writer.name(KEY_AUTHENTICATION_TYPE).value(serverSettings.authenticationType.name)
+        writer.name(KEY_USERNAME).value(serverSettings.username)
+        writer.name(KEY_PASSWORD).value(serverSettings.password)
+        writer.name(KEY_CLIENT_CERTIFICATE_ALIAS).value(serverSettings.clientCertificateAlias)
+
+        for ((key, value) in serverSettings.extra) {
+            writer.name(key).value(value)
+        }
+
+        writer.endObject()
+    }
+
+    private fun JsonReader.nextStringOrNull(): String? {
+        return if (peek() == Token.NULL) nextNull() else nextString()
+    }
+}

app/core/src/main/java/com/fsck/k9/StrictMode.kt

@@ -0,0 +1,44 @@
+package com.fsck.k9
+
+import android.os.Build
+import android.os.StrictMode
+import android.os.StrictMode.ThreadPolicy
+import android.os.StrictMode.VmPolicy
+
+fun enableStrictMode() {
+    StrictMode.setThreadPolicy(createThreadPolicy())
+    StrictMode.setVmPolicy(createVmPolicy())
+}
+
+private fun createThreadPolicy(): ThreadPolicy {
+    return ThreadPolicy.Builder()
+        .detectAll()
+        .penaltyLog()
+        .build()
+}
+
+private fun createVmPolicy(): VmPolicy {
+    return VmPolicy.Builder()
+        .detectActivityLeaks()
+        .detectLeakedClosableObjects()
+        .detectLeakedRegistrationObjects()
+        .detectFileUriExposure()
+        .detectLeakedSqlLiteObjects()
+        .apply {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                detectContentUriWithoutPermission()
+
+                // Disabled because we currently don't use tagged sockets; so this would generate a lot of noise
+                // detectUntaggedSockets()
+            }
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+                detectCredentialProtectedWhileLocked()
+            }
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+                detectIncorrectContextUse()
+                detectUnsafeIntentLaunch()
+            }
+        }
+        .penaltyLog()
+        .build()
+}

app/core/src/main/java/com/fsck/k9/SwipeAction.kt

@@ -0,0 +1,12 @@
+package com.fsck.k9
+
+enum class SwipeAction(val removesItem: Boolean) {
+    None(removesItem = false),
+    ToggleSelection(removesItem = false),
+    ToggleRead(removesItem = false),
+    ToggleStar(removesItem = false),
+    Archive(removesItem = true),
+    Delete(removesItem = true),
+    Spam(removesItem = true),
+    Move(removesItem = true)
+}

app/core/src/main/java/com/fsck/k9/TimberLogger.kt

@@ -0,0 +1,121 @@
+package com.fsck.k9
+
+import android.os.Build
+import com.fsck.k9.logging.Logger
+import java.util.regex.Pattern
+import timber.log.Timber
+
+class TimberLogger : Logger {
+    override fun v(message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.v(message, *args)
+    }
+
+    override fun v(t: Throwable?, message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.v(t, message, *args)
+    }
+
+    override fun v(t: Throwable?) {
+        setTimberTag()
+        Timber.v(t)
+    }
+
+    override fun d(message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.d(message, *args)
+    }
+
+    override fun d(t: Throwable?, message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.d(t, message, *args)
+    }
+
+    override fun d(t: Throwable?) {
+        setTimberTag()
+        Timber.d(t)
+    }
+
+    override fun i(message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.i(message, *args)
+    }
+
+    override fun i(t: Throwable?, message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.i(t, message, *args)
+    }
+
+    override fun i(t: Throwable?) {
+        setTimberTag()
+        Timber.i(t)
+    }
+
+    override fun w(message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.w(message, *args)
+    }
+
+    override fun w(t: Throwable?, message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.w(t, message, *args)
+    }
+
+    override fun w(t: Throwable?) {
+        setTimberTag()
+        Timber.w(t)
+    }
+
+    override fun e(message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.e(message, *args)
+    }
+
+    override fun e(t: Throwable?, message: String?, vararg args: Any?) {
+        setTimberTag()
+        Timber.e(t, message, *args)
+    }
+
+    override fun e(t: Throwable?) {
+        setTimberTag()
+        Timber.e(t)
+    }
+
+    private fun setTimberTag() {
+        val tag = Throwable().stackTrace
+            .first { it.className !in IGNORE_CLASSES }
+            .let(::createStackElementTag)
+
+        // We explicitly set a tag, otherwise Timber will always derive the tag "TimberLogger".
+        Timber.tag(tag)
+    }
+
+    private fun createStackElementTag(element: StackTraceElement): String {
+        var tag = element.className.substringAfterLast('.')
+        val matcher = ANONYMOUS_CLASS.matcher(tag)
+        if (matcher.find()) {
+            tag = matcher.replaceAll("")
+        }
+
+        // Tag length limit was removed in API 26.
+        return if (tag.length <= MAX_TAG_LENGTH || Build.VERSION.SDK_INT >= 26) {
+            tag
+        } else {
+            tag.substring(0, MAX_TAG_LENGTH)
+        }
+    }
+
+    companion object {
+        private const val MAX_TAG_LENGTH = 23
+        private val ANONYMOUS_CLASS = Pattern.compile("(\\$\\d+)+$")
+
+        private val IGNORE_CLASSES = setOf(
+            Timber::class.java.name,
+            Timber.Forest::class.java.name,
+            Timber.Tree::class.java.name,
+            Timber.DebugTree::class.java.name,
+            TimberLogger::class.java.name,
+            com.fsck.k9.logging.Timber::class.java.name
+        )
+    }
+}

app/core/src/main/java/com/fsck/k9/UiDensity.kt

@@ -0,0 +1,7 @@
+package com.fsck.k9
+
+enum class UiDensity {
+    Compact,
+    Default,
+    Relaxed,
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptDraftStateHeader.kt

@@ -0,0 +1,70 @@
+package com.fsck.k9.autocrypt
+
+import com.fsck.k9.message.CryptoStatus
+
+data class AutocryptDraftStateHeader(
+    val isEncrypt: Boolean,
+    val isSignOnly: Boolean,
+    val isReply: Boolean,
+    val isByChoice: Boolean,
+    val isPgpInline: Boolean,
+    val parameters: Map<String, String> = mapOf()
+) {
+
+    fun toHeaderValue(): String {
+        val builder = StringBuilder()
+
+        builder.append(AutocryptDraftStateHeader.PARAM_ENCRYPT)
+        builder.append(if (isEncrypt) "=yes; " else "=no; ")
+
+        if (isReply) {
+            builder.append(AutocryptDraftStateHeader.PARAM_IS_REPLY).append("=yes; ")
+        }
+        if (isSignOnly) {
+            builder.append(AutocryptDraftStateHeader.PARAM_SIGN_ONLY).append("=yes; ")
+        }
+        if (isByChoice) {
+            builder.append(AutocryptDraftStateHeader.PARAM_BY_CHOICE).append("=yes; ")
+        }
+        if (isPgpInline) {
+            builder.append(AutocryptDraftStateHeader.PARAM_PGP_INLINE).append("=yes; ")
+        }
+
+        return builder.toString()
+    }
+
+    companion object {
+        const val AUTOCRYPT_DRAFT_STATE_HEADER = "Autocrypt-Draft-State"
+
+        const val PARAM_ENCRYPT = "encrypt"
+
+        const val PARAM_IS_REPLY = "_is-reply-to-encrypted"
+        const val PARAM_BY_CHOICE = "_by-choice"
+        const val PARAM_PGP_INLINE = "_pgp-inline"
+        const val PARAM_SIGN_ONLY = "_sign-only"
+
+        const val VALUE_YES = "yes"
+
+        @JvmStatic
+        fun fromCryptoStatus(cryptoStatus: CryptoStatus): AutocryptDraftStateHeader {
+            if (cryptoStatus.isSignOnly) {
+                return AutocryptDraftStateHeader(
+                    false,
+                    true,
+                    cryptoStatus.isReplyToEncrypted,
+                    cryptoStatus.isUserChoice(),
+                    cryptoStatus.isPgpInlineModeEnabled,
+                    mapOf()
+                )
+            }
+            return AutocryptDraftStateHeader(
+                cryptoStatus.isEncryptionEnabled,
+                false,
+                cryptoStatus.isReplyToEncrypted,
+                cryptoStatus.isUserChoice(),
+                cryptoStatus.isPgpInlineModeEnabled,
+                mapOf()
+            )
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptDraftStateHeaderParser.kt

@@ -0,0 +1,40 @@
+package com.fsck.k9.autocrypt
+
+import com.fsck.k9.mail.internet.MimeUtility
+
+class AutocryptDraftStateHeaderParser internal constructor() {
+
+    fun parseAutocryptDraftStateHeader(headerValue: String): AutocryptDraftStateHeader? {
+        val parameters = MimeUtility.getAllHeaderParameters(headerValue)
+
+        val isEncryptStr = parameters.remove(AutocryptDraftStateHeader.PARAM_ENCRYPT) ?: return null
+        val isEncrypt = isEncryptStr == AutocryptDraftStateHeader.VALUE_YES
+
+        val isSignOnlyStr = parameters.remove(AutocryptDraftStateHeader.PARAM_SIGN_ONLY)
+        val isSignOnly = isSignOnlyStr == AutocryptDraftStateHeader.VALUE_YES
+
+        val isReplyStr = parameters.remove(AutocryptDraftStateHeader.PARAM_IS_REPLY)
+        val isReply = isReplyStr == AutocryptDraftStateHeader.VALUE_YES
+
+        val isByChoiceStr = parameters.remove(AutocryptDraftStateHeader.PARAM_BY_CHOICE)
+        val isByChoice = isByChoiceStr == AutocryptDraftStateHeader.VALUE_YES
+
+        val isPgpInlineStr = parameters.remove(AutocryptDraftStateHeader.PARAM_PGP_INLINE)
+        val isPgpInline = isPgpInlineStr == AutocryptDraftStateHeader.VALUE_YES
+
+        if (hasCriticalParameters(parameters)) {
+            return null
+        }
+
+        return AutocryptDraftStateHeader(isEncrypt, isSignOnly, isReply, isByChoice, isPgpInline, parameters)
+    }
+
+    private fun hasCriticalParameters(parameters: Map<String, String>): Boolean {
+        for (parameterName in parameters.keys) {
+            if (!parameterName.startsWith("_")) {
+                return true
+            }
+        }
+        return false
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptGossipHeader.java

@@ -0,0 +1,60 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.util.Arrays;
+
+import androidx.annotation.NonNull;
+
+
+class AutocryptGossipHeader {
+    static final String AUTOCRYPT_GOSSIP_HEADER = "Autocrypt-Gossip";
+
+    private static final String AUTOCRYPT_PARAM_ADDR = "addr";
+    private static final String AUTOCRYPT_PARAM_KEY_DATA = "keydata";
+
+
+    @NonNull
+    final byte[] keyData;
+    @NonNull
+    final String addr;
+
+    AutocryptGossipHeader(@NonNull String addr, @NonNull byte[] keyData) {
+        this.addr = addr;
+        this.keyData = keyData;
+    }
+
+    String toRawHeaderString() {
+        StringBuilder builder = new StringBuilder();
+
+        builder.append(AutocryptGossipHeader.AUTOCRYPT_GOSSIP_HEADER).append(": ");
+        builder.append(AutocryptGossipHeader.AUTOCRYPT_PARAM_ADDR).append('=').append(addr).append("; ");
+        builder.append(AutocryptGossipHeader.AUTOCRYPT_PARAM_KEY_DATA).append('=');
+        builder.append(AutocryptHeader.createFoldedBase64KeyData(keyData));
+
+        return builder.toString();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        AutocryptGossipHeader that = (AutocryptGossipHeader) o;
+
+        if (!Arrays.equals(keyData, that.keyData)) {
+            return false;
+        }
+        return addr.equals(that.addr);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Arrays.hashCode(keyData);
+        result = 31 * result + addr.hashCode();
+        return result;
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptGossipHeaderParser.java

@@ -0,0 +1,95 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import com.fsck.k9.mail.Part;
+import com.fsck.k9.mail.internet.MimeUtility;
+import okio.ByteString;
+import timber.log.Timber;
+
+
+class AutocryptGossipHeaderParser {
+    private static final AutocryptGossipHeaderParser INSTANCE = new AutocryptGossipHeaderParser();
+
+
+    public static AutocryptGossipHeaderParser getInstance() {
+        return INSTANCE;
+    }
+
+    private AutocryptGossipHeaderParser() { }
+
+
+    List<AutocryptGossipHeader> getAllAutocryptGossipHeaders(Part part) {
+        String[] headers = part.getHeader(AutocryptGossipHeader.AUTOCRYPT_GOSSIP_HEADER);
+        List<AutocryptGossipHeader> autocryptHeaders = parseAllAutocryptGossipHeaders(headers);
+
+        return Collections.unmodifiableList(autocryptHeaders);
+    }
+
+    @Nullable
+    @VisibleForTesting
+    AutocryptGossipHeader parseAutocryptGossipHeader(String headerValue) {
+        Map<String,String> parameters = MimeUtility.getAllHeaderParameters(headerValue);
+
+        String type = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_TYPE);
+        if (type != null && !type.equals(AutocryptHeader.AUTOCRYPT_TYPE_1)) {
+            Timber.e("autocrypt: unsupported type parameter %s", type);
+            return null;
+        }
+
+        String base64KeyData = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_KEY_DATA);
+        if (base64KeyData == null) {
+            Timber.e("autocrypt: missing key parameter");
+            return null;
+        }
+
+        ByteString byteString = ByteString.decodeBase64(base64KeyData);
+        if (byteString == null) {
+            Timber.e("autocrypt: error parsing base64 data");
+            return null;
+        }
+
+        String addr = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_ADDR);
+        if (addr == null) {
+            Timber.e("autocrypt: no to header!");
+            return null;
+        }
+
+        if (hasCriticalParameters(parameters)) {
+            return null;
+        }
+
+        return new AutocryptGossipHeader(addr, byteString.toByteArray());
+    }
+
+    private boolean hasCriticalParameters(Map<String, String> parameters) {
+        for (String parameterName : parameters.keySet()) {
+            if (parameterName != null && !parameterName.startsWith("_")) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @NonNull
+    private List<AutocryptGossipHeader> parseAllAutocryptGossipHeaders(String[] headers) {
+        ArrayList<AutocryptGossipHeader> autocryptHeaders = new ArrayList<>();
+        for (String header : headers) {
+            AutocryptGossipHeader autocryptHeader = parseAutocryptGossipHeader(header);
+            if (autocryptHeader == null) {
+                Timber.e("Encountered malformed autocrypt-gossip header - skipping!");
+                continue;
+            }
+            autocryptHeaders.add(autocryptHeader);
+        }
+        return autocryptHeaders;
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptHeader.java

@@ -0,0 +1,102 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.util.Arrays;
+import java.util.Map;
+
+import androidx.annotation.NonNull;
+
+import okio.ByteString;
+
+
+class AutocryptHeader {
+    static final String AUTOCRYPT_HEADER = "Autocrypt";
+
+    static final String AUTOCRYPT_PARAM_ADDR = "addr";
+    static final String AUTOCRYPT_PARAM_KEY_DATA = "keydata";
+
+    static final String AUTOCRYPT_PARAM_TYPE = "type";
+    static final String AUTOCRYPT_TYPE_1 = "1";
+
+    static final String AUTOCRYPT_PARAM_PREFER_ENCRYPT = "prefer-encrypt";
+    static final String AUTOCRYPT_PREFER_ENCRYPT_MUTUAL = "mutual";
+
+    private static final int HEADER_LINE_LENGTH = 76;
+
+
+    @NonNull
+    final byte[] keyData;
+    @NonNull
+    final String addr;
+    @NonNull
+    final Map<String,String> parameters;
+    final boolean isPreferEncryptMutual;
+
+    AutocryptHeader(@NonNull Map<String, String> parameters, @NonNull String addr,
+            @NonNull byte[] keyData, boolean isPreferEncryptMutual) {
+        this.parameters = parameters;
+        this.addr = addr;
+        this.keyData = keyData;
+        this.isPreferEncryptMutual = isPreferEncryptMutual;
+    }
+
+    String toRawHeaderString() {
+        // TODO we don't properly fold lines here. if we want to support parameters, we need to do that somehow
+        if (!parameters.isEmpty()) {
+            throw new UnsupportedOperationException("arbitrary parameters not supported");
+        }
+
+        StringBuilder builder = new StringBuilder();
+        builder.append(AutocryptHeader.AUTOCRYPT_HEADER).append(": ");
+        builder.append(AutocryptHeader.AUTOCRYPT_PARAM_ADDR).append('=').append(addr).append("; ");
+        if (isPreferEncryptMutual) {
+            builder.append(AutocryptHeader.AUTOCRYPT_PARAM_PREFER_ENCRYPT)
+                    .append('=').append(AutocryptHeader.AUTOCRYPT_PREFER_ENCRYPT_MUTUAL).append("; ");
+        }
+        builder.append(AutocryptHeader.AUTOCRYPT_PARAM_KEY_DATA).append("=");
+        builder.append(createFoldedBase64KeyData(keyData));
+
+        return builder.toString();
+    }
+
+    static String createFoldedBase64KeyData(byte[] keyData) {
+        String base64KeyData = ByteString.of(keyData).base64();
+        StringBuilder result = new StringBuilder();
+
+        for (int i = 0, base64Length = base64KeyData.length(); i < base64Length; i += HEADER_LINE_LENGTH) {
+            if (i + HEADER_LINE_LENGTH <= base64Length) {
+                result.append("\r\n ");
+                result.append(base64KeyData, i, i + HEADER_LINE_LENGTH);
+            } else {
+                result.append("\r\n ");
+                result.append(base64KeyData, i, base64Length);
+            }
+        }
+
+        return result.toString();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        AutocryptHeader that = (AutocryptHeader) o;
+
+        return isPreferEncryptMutual == that.isPreferEncryptMutual && Arrays.equals(keyData, that.keyData)
+                && addr.equals(that.addr) && parameters.equals(that.parameters);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Arrays.hashCode(keyData);
+        result = 31 * result + addr.hashCode();
+        result = 31 * result + parameters.hashCode();
+        result = 31 * result + (isPreferEncryptMutual ? 1 : 0);
+        return result;
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptHeaderParser.java

@@ -0,0 +1,99 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.util.ArrayList;
+import java.util.Map;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.internet.MimeUtility;
+import okio.ByteString;
+import timber.log.Timber;
+
+
+class AutocryptHeaderParser {
+    private static final AutocryptHeaderParser INSTANCE = new AutocryptHeaderParser();
+
+
+    public static AutocryptHeaderParser getInstance() {
+        return INSTANCE;
+    }
+
+    private AutocryptHeaderParser() { }
+
+
+    @Nullable
+    AutocryptHeader getValidAutocryptHeader(Message currentMessage) {
+        String[] headers = currentMessage.getHeader(AutocryptHeader.AUTOCRYPT_HEADER);
+        ArrayList<AutocryptHeader> autocryptHeaders = parseAllAutocryptHeaders(headers);
+
+        boolean isSingleValidHeader = autocryptHeaders.size() == 1;
+        return isSingleValidHeader ? autocryptHeaders.get(0) : null;
+    }
+
+    @Nullable
+    @VisibleForTesting
+    AutocryptHeader parseAutocryptHeader(String headerValue) {
+        Map<String,String> parameters = MimeUtility.getAllHeaderParameters(headerValue);
+
+        String type = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_TYPE);
+        if (type != null && !type.equals(AutocryptHeader.AUTOCRYPT_TYPE_1)) {
+            Timber.e("autocrypt: unsupported type parameter %s", type);
+            return null;
+        }
+
+        String base64KeyData = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_KEY_DATA);
+        if (base64KeyData == null) {
+            Timber.e("autocrypt: missing key parameter");
+            return null;
+        }
+
+        ByteString byteString = ByteString.decodeBase64(base64KeyData);
+        if (byteString == null) {
+            Timber.e("autocrypt: error parsing base64 data");
+            return null;
+        }
+
+        String to = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_ADDR);
+        if (to == null) {
+            Timber.e("autocrypt: no to header!");
+            return null;
+        }
+
+        boolean isPreferEncryptMutual = false;
+        String preferEncrypt = parameters.remove(AutocryptHeader.AUTOCRYPT_PARAM_PREFER_ENCRYPT);
+        if (AutocryptHeader.AUTOCRYPT_PREFER_ENCRYPT_MUTUAL.equalsIgnoreCase(preferEncrypt)) {
+            isPreferEncryptMutual = true;
+        }
+
+        if (hasCriticalParameters(parameters)) {
+            return null;
+        }
+
+        return new AutocryptHeader(parameters, to, byteString.toByteArray(), isPreferEncryptMutual);
+    }
+
+    private boolean hasCriticalParameters(Map<String, String> parameters) {
+        for (String parameterName : parameters.keySet()) {
+            if (parameterName != null && !parameterName.startsWith("_")) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @NonNull
+    private ArrayList<AutocryptHeader> parseAllAutocryptHeaders(String[] headers) {
+        ArrayList<AutocryptHeader> autocryptHeaders = new ArrayList<>();
+        for (String header : headers) {
+            AutocryptHeader autocryptHeader = parseAutocryptHeader(header);
+            if (autocryptHeader != null) {
+                autocryptHeaders.add(autocryptHeader);
+            }
+        }
+        return autocryptHeaders;
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptOpenPgpApiInteractor.java

@@ -0,0 +1,44 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+
+import android.content.Intent;
+
+import org.openintents.openpgp.util.OpenPgpApi;
+
+
+public class AutocryptOpenPgpApiInteractor {
+    public static AutocryptOpenPgpApiInteractor getInstance() {
+        return new AutocryptOpenPgpApiInteractor();
+    }
+
+    private AutocryptOpenPgpApiInteractor() { }
+
+    public byte[] getKeyMaterialForKeyId(OpenPgpApi openPgpApi, long keyId, String minimizeForUserId) {
+        Intent retrieveKeyIntent = new Intent(OpenPgpApi.ACTION_GET_KEY);
+        retrieveKeyIntent.putExtra(OpenPgpApi.EXTRA_KEY_ID, keyId);
+        return getKeyMaterialFromApi(openPgpApi, retrieveKeyIntent, minimizeForUserId);
+    }
+
+    public byte[] getKeyMaterialForUserId(OpenPgpApi openPgpApi, String userId) {
+        Intent retrieveKeyIntent = new Intent(OpenPgpApi.ACTION_GET_KEY);
+        retrieveKeyIntent.putExtra(OpenPgpApi.EXTRA_USER_ID, userId);
+        return getKeyMaterialFromApi(openPgpApi, retrieveKeyIntent, userId);
+    }
+
+    private byte[] getKeyMaterialFromApi(OpenPgpApi openPgpApi, Intent retrieveKeyIntent, String userId) {
+        retrieveKeyIntent.putExtra(OpenPgpApi.EXTRA_MINIMIZE, true);
+        retrieveKeyIntent.putExtra(OpenPgpApi.EXTRA_MINIMIZE_USER_ID, userId);
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        Intent result = openPgpApi.executeApi(retrieveKeyIntent, (InputStream) null, baos);
+
+        if (result.getIntExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_ERROR) ==
+                OpenPgpApi.RESULT_CODE_SUCCESS) {
+            return baos.toByteArray();
+        } else{
+            return null;
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptOperations.java

@@ -0,0 +1,164 @@
+package com.fsck.k9.autocrypt;
+
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Date;
+import java.util.List;
+import java.util.Locale;
+
+import android.content.Intent;
+import android.os.Bundle;
+import androidx.annotation.Nullable;
+
+import com.fsck.k9.mail.Address;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.Message.RecipientType;
+import com.fsck.k9.mail.internet.MimeBodyPart;
+import org.openintents.openpgp.AutocryptPeerUpdate;
+import org.openintents.openpgp.util.OpenPgpApi;
+
+
+public class AutocryptOperations {
+    private final AutocryptHeaderParser autocryptHeaderParser;
+    private final AutocryptGossipHeaderParser autocryptGossipHeaderParser;
+
+
+    public static AutocryptOperations getInstance() {
+        AutocryptHeaderParser autocryptHeaderParser = AutocryptHeaderParser.getInstance();
+        AutocryptGossipHeaderParser autocryptGossipHeaderParser = AutocryptGossipHeaderParser.getInstance();
+        return new AutocryptOperations(autocryptHeaderParser, autocryptGossipHeaderParser);
+    }
+
+
+    private AutocryptOperations(AutocryptHeaderParser autocryptHeaderParser,
+            AutocryptGossipHeaderParser autocryptGossipHeaderParser) {
+        this.autocryptHeaderParser = autocryptHeaderParser;
+        this.autocryptGossipHeaderParser = autocryptGossipHeaderParser;
+    }
+
+    public boolean addAutocryptPeerUpdateToIntentIfPresent(Message currentMessage, Intent intent) {
+        AutocryptHeader autocryptHeader = autocryptHeaderParser.getValidAutocryptHeader(currentMessage);
+        if (autocryptHeader == null) {
+            return false;
+        }
+
+        String messageFromAddress = currentMessage.getFrom()[0].getAddress();
+        if (!autocryptHeader.addr.equalsIgnoreCase(messageFromAddress)) {
+            return false;
+        }
+
+        Date messageDate = currentMessage.getSentDate();
+        Date internalDate = currentMessage.getInternalDate();
+        Date effectiveDate = messageDate.before(internalDate) ? messageDate : internalDate;
+
+        AutocryptPeerUpdate data = AutocryptPeerUpdate.create(
+                autocryptHeader.keyData, effectiveDate, autocryptHeader.isPreferEncryptMutual);
+        intent.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_ID, messageFromAddress);
+        intent.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_UPDATE, data);
+        return true;
+    }
+
+    public boolean addAutocryptGossipUpdateToIntentIfPresent(Message message, MimeBodyPart decryptedPart, Intent intent) {
+        Bundle updates = createGossipUpdateBundle(message, decryptedPart);
+
+        if (updates == null) {
+            return false;
+        }
+
+        intent.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_GOSSIP_UPDATES, updates);
+        return true;
+    }
+
+    @Nullable
+    private Bundle createGossipUpdateBundle(Message message, MimeBodyPart decryptedPart) {
+        List<String> gossipAcceptedAddresses = getGossipAcceptedAddresses(message);
+        if (gossipAcceptedAddresses.isEmpty()) {
+            return null;
+        }
+
+        List<AutocryptGossipHeader> autocryptGossipHeaders =
+                autocryptGossipHeaderParser.getAllAutocryptGossipHeaders(decryptedPart);
+        if (autocryptGossipHeaders.isEmpty()) {
+            return null;
+        }
+
+        Date messageDate = message.getSentDate();
+        Date internalDate = message.getInternalDate();
+        Date effectiveDate = messageDate.before(internalDate) ? messageDate : internalDate;
+
+        return createGossipUpdateBundle(gossipAcceptedAddresses, autocryptGossipHeaders, effectiveDate);
+    }
+
+    @Nullable
+    private Bundle createGossipUpdateBundle(List<String> gossipAcceptedAddresses,
+            List<AutocryptGossipHeader> autocryptGossipHeaders, Date effectiveDate) {
+        Bundle updates = new Bundle();
+        for (AutocryptGossipHeader autocryptGossipHeader : autocryptGossipHeaders) {
+            String normalizedAddress = autocryptGossipHeader.addr.toLowerCase(Locale.ROOT);
+            boolean isAcceptedAddress = gossipAcceptedAddresses.contains(normalizedAddress);
+            if (!isAcceptedAddress) {
+                continue;
+            }
+
+            AutocryptPeerUpdate update = AutocryptPeerUpdate.create(autocryptGossipHeader.keyData, effectiveDate, false);
+            updates.putParcelable(autocryptGossipHeader.addr, update);
+        }
+        if (updates.isEmpty()) {
+            return null;
+        }
+        return updates;
+    }
+
+    private List<String> getGossipAcceptedAddresses(Message message) {
+        ArrayList<String> result = new ArrayList<>();
+
+        addRecipientsToList(result, message, RecipientType.TO);
+        addRecipientsToList(result, message, RecipientType.CC);
+        removeRecipientsFromList(result, message, RecipientType.DELIVERED_TO);
+
+        return Collections.unmodifiableList(result);
+    }
+
+    private void addRecipientsToList(ArrayList<String> result, Message message, RecipientType recipientType) {
+        for (Address address : message.getRecipients(recipientType)) {
+            String addr = address.getAddress();
+            if (addr != null) {
+                result.add(addr.toLowerCase(Locale.ROOT));
+            }
+        }
+    }
+
+    private void removeRecipientsFromList(ArrayList<String> result, Message message, RecipientType recipientType) {
+        for (Address address : message.getRecipients(recipientType)) {
+            String addr = address.getAddress();
+            if (addr != null) {
+                result.remove(addr);
+            }
+        }
+    }
+
+    public boolean hasAutocryptHeader(Message currentMessage) {
+        return currentMessage.getHeader(AutocryptHeader.AUTOCRYPT_HEADER).length > 0;
+    }
+
+    public boolean hasAutocryptGossipHeader(MimeBodyPart part) {
+        return part.getHeader(AutocryptGossipHeader.AUTOCRYPT_GOSSIP_HEADER).length > 0;
+    }
+
+    public void addAutocryptHeaderToMessage(Message message, byte[] keyData,
+            String autocryptAddress, boolean preferEncryptMutual) {
+        AutocryptHeader autocryptHeader = new AutocryptHeader(
+                Collections.<String,String>emptyMap(), autocryptAddress, keyData, preferEncryptMutual);
+        String rawAutocryptHeader = autocryptHeader.toRawHeaderString();
+
+        message.addRawHeader(AutocryptHeader.AUTOCRYPT_HEADER, rawAutocryptHeader);
+    }
+
+    public void addAutocryptGossipHeaderToPart(MimeBodyPart part, byte[] keyData, String autocryptAddress) {
+        AutocryptGossipHeader autocryptGossipHeader = new AutocryptGossipHeader(autocryptAddress, keyData);
+        String rawAutocryptHeader = autocryptGossipHeader.toRawHeaderString();
+
+        part.addRawHeader(AutocryptGossipHeader.AUTOCRYPT_GOSSIP_HEADER, rawAutocryptHeader);
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptStringProvider.kt

@@ -0,0 +1,6 @@
+package com.fsck.k9.autocrypt
+
+interface AutocryptStringProvider {
+    fun transferMessageSubject(): String
+    fun transferMessageBody(): String
+}

app/core/src/main/java/com/fsck/k9/autocrypt/AutocryptTransferMessageCreator.kt

@@ -0,0 +1,50 @@
+package com.fsck.k9.autocrypt
+
+import com.fsck.k9.K9
+import com.fsck.k9.mail.Address
+import com.fsck.k9.mail.Flag
+import com.fsck.k9.mail.Message
+import com.fsck.k9.mail.MessagingException
+import com.fsck.k9.mail.internet.MimeBodyPart
+import com.fsck.k9.mail.internet.MimeHeader
+import com.fsck.k9.mail.internet.MimeMessage
+import com.fsck.k9.mail.internet.MimeMessageHelper
+import com.fsck.k9.mail.internet.MimeMultipart
+import com.fsck.k9.mail.internet.TextBody
+import com.fsck.k9.mailstore.BinaryMemoryBody
+import java.util.Date
+
+class AutocryptTransferMessageCreator(private val stringProvider: AutocryptStringProvider) {
+    fun createAutocryptTransferMessage(data: ByteArray, address: Address): Message {
+        try {
+            val subjectText = stringProvider.transferMessageSubject()
+            val messageText = stringProvider.transferMessageBody()
+
+            val textBodyPart = MimeBodyPart.create(TextBody(messageText))
+            val dataBodyPart = MimeBodyPart.create(BinaryMemoryBody(data, "7bit"))
+            dataBodyPart.setHeader(MimeHeader.HEADER_CONTENT_TYPE, "application/autocrypt-setup")
+            dataBodyPart.setHeader(MimeHeader.HEADER_CONTENT_DISPOSITION, "attachment; filename=\"autocrypt-setup-message\"")
+
+            val messageBody = MimeMultipart.newInstance()
+            messageBody.addBodyPart(textBodyPart)
+            messageBody.addBodyPart(dataBodyPart)
+
+            val message = MimeMessage.create()
+            MimeMessageHelper.setBody(message, messageBody)
+
+            val nowDate = Date()
+
+            message.setFlag(Flag.X_DOWNLOADED_FULL, true)
+            message.subject = subjectText
+            message.setHeader("Autocrypt-Setup-Message", "v1")
+            message.internalDate = nowDate
+            message.addSentDate(nowDate, K9.isHideTimeZone)
+            message.setFrom(address)
+            message.setHeader("To", address.toEncodedString())
+
+            return message
+        } catch (e: MessagingException) {
+            throw AssertionError(e)
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/autocrypt/KoinModule.kt

@@ -0,0 +1,8 @@
+package com.fsck.k9.autocrypt
+
+import org.koin.dsl.module
+
+val autocryptModule = module {
+    single { AutocryptTransferMessageCreator(get()) }
+    single { AutocryptDraftStateHeaderParser() }
+}

app/core/src/main/java/com/fsck/k9/backend/BackendFactory.kt

@@ -0,0 +1,8 @@
+package com.fsck.k9.backend
+
+import com.fsck.k9.Account
+import com.fsck.k9.backend.api.Backend
+
+interface BackendFactory {
+    fun createBackend(account: Account): Backend
+}

app/core/src/main/java/com/fsck/k9/backend/BackendManager.kt

@@ -0,0 +1,75 @@
+package com.fsck.k9.backend
+
+import com.fsck.k9.Account
+import com.fsck.k9.backend.api.Backend
+import com.fsck.k9.mail.ServerSettings
+import java.util.concurrent.CopyOnWriteArraySet
+
+class BackendManager(private val backendFactories: Map<String, BackendFactory>) {
+    private val backendCache = mutableMapOf<String, BackendContainer>()
+    private val listeners = CopyOnWriteArraySet<BackendChangedListener>()
+
+    fun getBackend(account: Account): Backend {
+        val newBackend = synchronized(backendCache) {
+            val container = backendCache[account.uuid]
+            if (container != null && isBackendStillValid(container, account)) {
+                return container.backend
+            }
+
+            createBackend(account).also { backend ->
+                backendCache[account.uuid] = BackendContainer(
+                    backend,
+                    account.incomingServerSettings,
+                    account.outgoingServerSettings
+                )
+            }
+        }
+
+        notifyListeners(account)
+
+        return newBackend
+    }
+
+    private fun isBackendStillValid(container: BackendContainer, account: Account): Boolean {
+        return container.incomingServerSettings == account.incomingServerSettings &&
+            container.outgoingServerSettings == account.outgoingServerSettings
+    }
+
+    fun removeBackend(account: Account) {
+        synchronized(backendCache) {
+            backendCache.remove(account.uuid)
+        }
+
+        notifyListeners(account)
+    }
+
+    private fun createBackend(account: Account): Backend {
+        val serverType = account.incomingServerSettings.type
+        val backendFactory = backendFactories[serverType] ?: error("Unsupported account type")
+        return backendFactory.createBackend(account)
+    }
+
+    fun addListener(listener: BackendChangedListener) {
+        listeners.add(listener)
+    }
+
+    fun removeListener(listener: BackendChangedListener) {
+        listeners.remove(listener)
+    }
+
+    private fun notifyListeners(account: Account) {
+        for (listener in listeners) {
+            listener.onBackendChanged(account)
+        }
+    }
+}
+
+private data class BackendContainer(
+    val backend: Backend,
+    val incomingServerSettings: ServerSettings,
+    val outgoingServerSettings: ServerSettings
+)
+
+fun interface BackendChangedListener {
+    fun onBackendChanged(account: Account)
+}

app/core/src/main/java/com/fsck/k9/contact/ContactIntentHelper.kt

@@ -0,0 +1,47 @@
+package com.fsck.k9.contact
+
+import android.content.Intent
+import android.net.Uri
+import android.provider.ContactsContract
+import com.fsck.k9.mail.Address
+
+object ContactIntentHelper {
+    @JvmStatic
+    fun getContactPickerIntent(): Intent {
+        return Intent(Intent.ACTION_PICK, ContactsContract.CommonDataKinds.Email.CONTENT_URI)
+    }
+
+    /**
+     * Get Intent to add information to an existing contact or add a new one.
+     *
+     * @param address An {@link Address} instance containing the email address
+     *              of the entity you want to add to the contacts. Optionally
+     *              the instance also contains the (display) name of that
+     *              entity.
+     */
+    fun getAddEmailContactIntent(address: Address): Intent {
+        return Intent(ContactsContract.Intents.SHOW_OR_CREATE_CONTACT).apply {
+            flags = Intent.FLAG_ACTIVITY_NEW_TASK
+            data = Uri.fromParts("mailto", address.address, null)
+            putExtra(ContactsContract.Intents.EXTRA_CREATE_DESCRIPTION, address.toString())
+
+            if (address.personal != null) {
+                putExtra(ContactsContract.Intents.Insert.NAME, address.personal)
+            }
+        }
+    }
+
+    /**
+     * Get Intent to add a phone number to an existing contact or add a new one.
+     *
+     * @param phoneNumber
+     *         The phone number to add to a contact, or to use when creating a new contact.
+     */
+    fun getAddPhoneContactIntent(phoneNumber: String): Intent {
+        return Intent(Intent.ACTION_INSERT_OR_EDIT).apply {
+            flags = Intent.FLAG_ACTIVITY_NEW_TASK
+            type = ContactsContract.Contacts.CONTENT_ITEM_TYPE
+            putExtra(ContactsContract.Intents.Insert.PHONE, Uri.decode(phoneNumber))
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/ControllerExtension.kt

@@ -0,0 +1,12 @@
+package com.fsck.k9.controller
+
+import com.fsck.k9.backend.BackendManager
+
+interface ControllerExtension {
+    fun init(controller: MessagingController, backendManager: BackendManager, controllerInternals: ControllerInternals)
+
+    interface ControllerInternals {
+        fun put(description: String, listener: MessagingListener?, runnable: Runnable)
+        fun putBackground(description: String, listener: MessagingListener?, runnable: Runnable)
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/DraftOperations.kt

@@ -0,0 +1,177 @@
+package com.fsck.k9.controller
+
+import com.fsck.k9.Account
+import com.fsck.k9.Account.Expunge
+import com.fsck.k9.K9
+import com.fsck.k9.backend.api.Backend
+import com.fsck.k9.controller.MessagingControllerCommands.PendingAppend
+import com.fsck.k9.controller.MessagingControllerCommands.PendingReplace
+import com.fsck.k9.mail.FetchProfile
+import com.fsck.k9.mail.Message
+import com.fsck.k9.mail.MessageDownloadState
+import com.fsck.k9.mail.MessagingException
+import com.fsck.k9.mailstore.LocalFolder
+import com.fsck.k9.mailstore.LocalMessage
+import com.fsck.k9.mailstore.MessageStoreManager
+import com.fsck.k9.mailstore.SaveMessageData
+import com.fsck.k9.mailstore.SaveMessageDataCreator
+import org.jetbrains.annotations.NotNull
+import timber.log.Timber
+
+internal class DraftOperations(
+    private val messagingController: @NotNull MessagingController,
+    private val messageStoreManager: @NotNull MessageStoreManager,
+    private val saveMessageDataCreator: SaveMessageDataCreator
+) {
+
+    fun saveDraft(
+        account: Account,
+        message: Message,
+        existingDraftId: Long?,
+        plaintextSubject: String?
+    ): Long? {
+        return try {
+            val draftsFolderId = account.draftsFolderId ?: error("No Drafts folder configured")
+
+            val messageId = if (messagingController.supportsUpload(account)) {
+                saveAndUploadDraft(account, message, draftsFolderId, existingDraftId, plaintextSubject)
+            } else {
+                saveDraftLocally(account, message, draftsFolderId, existingDraftId, plaintextSubject)
+            }
+
+            messageId
+        } catch (e: MessagingException) {
+            Timber.e(e, "Unable to save message as draft.")
+            null
+        }
+    }
+
+    private fun saveAndUploadDraft(
+        account: Account,
+        message: Message,
+        folderId: Long,
+        existingDraftId: Long?,
+        subject: String?
+    ): Long {
+        val messageStore = messageStoreManager.getMessageStore(account)
+
+        val messageId = messageStore.saveLocalMessage(folderId, message.toSaveMessageData(subject))
+
+        val previousDraftMessage = if (existingDraftId != null) {
+            val localStore = messagingController.getLocalStoreOrThrow(account)
+            val localFolder = localStore.getFolder(folderId)
+            localFolder.open()
+
+            localFolder.getMessage(existingDraftId)
+        } else {
+            null
+        }
+
+        if (previousDraftMessage != null) {
+            previousDraftMessage.delete()
+
+            val deleteMessageId = previousDraftMessage.databaseId
+            val command = PendingReplace.create(folderId, messageId, deleteMessageId)
+            messagingController.queuePendingCommand(account, command)
+        } else {
+            val fakeMessageServerId = messageStore.getMessageServerId(messageId)
+            if (fakeMessageServerId != null) {
+                val command = PendingAppend.create(folderId, fakeMessageServerId)
+                messagingController.queuePendingCommand(account, command)
+            }
+        }
+
+        messagingController.processPendingCommands(account)
+
+        return messageId
+    }
+
+    private fun saveDraftLocally(
+        account: Account,
+        message: Message,
+        folderId: Long,
+        existingDraftId: Long?,
+        plaintextSubject: String?
+    ): Long {
+        val messageStore = messageStoreManager.getMessageStore(account)
+        val messageData = message.toSaveMessageData(plaintextSubject)
+
+        return messageStore.saveLocalMessage(folderId, messageData, existingDraftId)
+    }
+
+    fun processPendingReplace(command: PendingReplace, account: Account) {
+        val localStore = messagingController.getLocalStoreOrThrow(account)
+        val localFolder = localStore.getFolder(command.folderId)
+        localFolder.open()
+
+        val backend = messagingController.getBackend(account)
+
+        val uploadMessageId = command.uploadMessageId
+        val localMessage = localFolder.getMessage(uploadMessageId)
+        if (localMessage == null) {
+            Timber.w("Couldn't find local copy of message to upload [ID: %d]", uploadMessageId)
+            return
+        } else if (!localMessage.uid.startsWith(K9.LOCAL_UID_PREFIX)) {
+            Timber.i("Message [ID: %d] to be uploaded already has a server ID set. Skipping upload.", uploadMessageId)
+        } else {
+            uploadMessage(backend, account, localFolder, localMessage)
+        }
+
+        deleteMessage(backend, account, localFolder, command.deleteMessageId)
+    }
+
+    private fun uploadMessage(
+        backend: Backend,
+        account: Account,
+        localFolder: LocalFolder,
+        localMessage: LocalMessage
+    ) {
+        val folderServerId = localFolder.serverId
+        Timber.d("Uploading message [ID: %d] to remote folder '%s'", localMessage.databaseId, folderServerId)
+
+        val fetchProfile = FetchProfile().apply {
+            add(FetchProfile.Item.BODY)
+        }
+        localFolder.fetch(listOf(localMessage), fetchProfile, null)
+
+        val messageServerId = backend.uploadMessage(folderServerId, localMessage)
+
+        if (messageServerId == null) {
+            Timber.w(
+                "Failed to get a server ID for the uploaded message. Removing local copy [ID: %d]",
+                localMessage.databaseId
+            )
+            localMessage.destroy()
+        } else {
+            val oldUid = localMessage.uid
+
+            localMessage.uid = messageServerId
+            localFolder.changeUid(localMessage)
+
+            for (listener in messagingController.listeners) {
+                listener.messageUidChanged(account, localFolder.databaseId, oldUid, localMessage.uid)
+            }
+        }
+    }
+
+    private fun deleteMessage(backend: Backend, account: Account, localFolder: LocalFolder, messageId: Long) {
+        val messageServerId = localFolder.getMessageUidById(messageId) ?: run {
+            Timber.i("Couldn't find local copy of message [ID: %d] to be deleted. Skipping delete.", messageId)
+            return
+        }
+
+        val messageServerIds = listOf(messageServerId)
+        val folderServerId = localFolder.serverId
+        backend.deleteMessages(folderServerId, messageServerIds)
+
+        if (backend.supportsExpunge && account.expungePolicy == Expunge.EXPUNGE_IMMEDIATELY) {
+            backend.expungeMessages(folderServerId, messageServerIds)
+        }
+
+        messagingController.destroyPlaceholderMessages(localFolder, messageServerIds)
+    }
+
+    private fun Message.toSaveMessageData(subject: String?): SaveMessageData {
+        return saveMessageDataCreator.createSaveMessageData(this, MessageDownloadState.FULL, subject)
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/KoinModule.kt

@@ -0,0 +1,36 @@
+package com.fsck.k9.controller
+
+import android.content.Context
+import com.fsck.k9.Preferences
+import com.fsck.k9.backend.BackendManager
+import com.fsck.k9.mailstore.LocalStoreProvider
+import com.fsck.k9.mailstore.MessageStoreManager
+import com.fsck.k9.mailstore.SaveMessageDataCreator
+import com.fsck.k9.mailstore.SpecialLocalFoldersCreator
+import com.fsck.k9.notification.NotificationController
+import com.fsck.k9.notification.NotificationStrategy
+import org.koin.core.qualifier.named
+import org.koin.dsl.module
+
+val controllerModule = module {
+    single {
+        MessagingController(
+            get<Context>(),
+            get<NotificationController>(),
+            get<NotificationStrategy>(),
+            get<LocalStoreProvider>(),
+            get<BackendManager>(),
+            get<Preferences>(),
+            get<MessageStoreManager>(),
+            get<SaveMessageDataCreator>(),
+            get<SpecialLocalFoldersCreator>(),
+            get(named("controllerExtensions"))
+        )
+    }
+    single<MessageCountsProvider> {
+        DefaultMessageCountsProvider(
+            preferences = get(),
+            messageStoreManager = get()
+        )
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MemorizingMessagingListener.java

@@ -0,0 +1,124 @@
+package com.fsck.k9.controller;
+
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import com.fsck.k9.Account;
+
+
+class MemorizingMessagingListener extends SimpleMessagingListener {
+    Map<String, Memory> memories = new HashMap<>(31);
+
+    synchronized void removeAccount(Account account) {
+        Iterator<Entry<String, Memory>> memIt = memories.entrySet().iterator();
+
+        while (memIt.hasNext()) {
+            Entry<String, Memory> memoryEntry = memIt.next();
+
+            String uuidForMemory = memoryEntry.getValue().account.getUuid();
+
+            if (uuidForMemory.equals(account.getUuid())) {
+                memIt.remove();
+            }
+        }
+    }
+
+    synchronized void refreshOther(MessagingListener other) {
+        if (other != null) {
+
+            Memory syncStarted = null;
+
+            for (Memory memory : memories.values()) {
+
+                if (memory.syncingState != null) {
+                    switch (memory.syncingState) {
+                        case STARTED:
+                            syncStarted = memory;
+                            break;
+                        case FINISHED:
+                            other.synchronizeMailboxFinished(memory.account, memory.folderId);
+                            break;
+                        case FAILED:
+                            other.synchronizeMailboxFailed(memory.account, memory.folderId,
+                                    memory.failureMessage);
+                            break;
+                    }
+                }
+            }
+            Memory somethingStarted = null;
+            if (syncStarted != null) {
+                other.synchronizeMailboxStarted(syncStarted.account, syncStarted.folderId);
+                somethingStarted = syncStarted;
+            }
+            if (somethingStarted != null && somethingStarted.folderTotal > 0) {
+                other.synchronizeMailboxProgress(somethingStarted.account, somethingStarted.folderId,
+                        somethingStarted.folderCompleted, somethingStarted.folderTotal);
+            }
+
+        }
+    }
+
+    @Override
+    public synchronized void synchronizeMailboxStarted(Account account, long folderId) {
+        Memory memory = getMemory(account, folderId);
+        memory.syncingState = MemorizingState.STARTED;
+        memory.folderCompleted = 0;
+        memory.folderTotal = 0;
+    }
+
+    @Override
+    public synchronized void synchronizeMailboxFinished(Account account, long folderId) {
+        Memory memory = getMemory(account, folderId);
+        memory.syncingState = MemorizingState.FINISHED;
+    }
+
+    @Override
+    public synchronized void synchronizeMailboxFailed(Account account, long folderId,
+            String message) {
+
+        Memory memory = getMemory(account, folderId);
+        memory.syncingState = MemorizingState.FAILED;
+        memory.failureMessage = message;
+    }
+
+    @Override
+    public synchronized void synchronizeMailboxProgress(Account account, long folderId, int completed,
+            int total) {
+        Memory memory = getMemory(account, folderId);
+        memory.folderCompleted = completed;
+        memory.folderTotal = total;
+    }
+
+    private Memory getMemory(Account account, long folderId) {
+        Memory memory = memories.get(getMemoryKey(account, folderId));
+        if (memory == null) {
+            memory = new Memory(account, folderId);
+            memories.put(getMemoryKey(memory.account, memory.folderId), memory);
+        }
+        return memory;
+    }
+
+    private static String getMemoryKey(Account account, long folderId) {
+        return account.getUuid() + ":" + folderId;
+    }
+
+    private enum MemorizingState { STARTED, FINISHED, FAILED }
+
+    private static class Memory {
+        Account account;
+        long folderId;
+        MemorizingState syncingState = null;
+        String failureMessage = null;
+
+        int folderCompleted = 0;
+        int folderTotal = 0;
+
+        Memory(Account account, long folderId) {
+            this.account = account;
+            this.folderId = folderId;
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MessageCountsProvider.kt

@@ -0,0 +1,76 @@
+package com.fsck.k9.controller
+
+import com.fsck.k9.Account
+import com.fsck.k9.Preferences
+import com.fsck.k9.mailstore.MessageStoreManager
+import com.fsck.k9.search.ConditionsTreeNode
+import com.fsck.k9.search.LocalSearch
+import com.fsck.k9.search.SearchAccount
+import com.fsck.k9.search.excludeSpecialFolders
+import com.fsck.k9.search.getAccounts
+import com.fsck.k9.search.limitToDisplayableFolders
+import timber.log.Timber
+
+interface MessageCountsProvider {
+    fun getMessageCounts(account: Account): MessageCounts
+    fun getMessageCounts(searchAccount: SearchAccount): MessageCounts
+    fun getUnreadMessageCount(account: Account, folderId: Long): Int
+}
+
+data class MessageCounts(val unread: Int, val starred: Int)
+
+internal class DefaultMessageCountsProvider(
+    private val preferences: Preferences,
+    private val messageStoreManager: MessageStoreManager
+) : MessageCountsProvider {
+    override fun getMessageCounts(account: Account): MessageCounts {
+        val search = LocalSearch().apply {
+            excludeSpecialFolders(account)
+            limitToDisplayableFolders(account)
+        }
+
+        return getMessageCounts(account, search.conditions)
+    }
+
+    override fun getMessageCounts(searchAccount: SearchAccount): MessageCounts {
+        val search = searchAccount.relatedSearch
+        val accounts = search.getAccounts(preferences)
+
+        var unreadCount = 0
+        var starredCount = 0
+        for (account in accounts) {
+            val accountMessageCount = getMessageCounts(account, search.conditions)
+            unreadCount += accountMessageCount.unread
+            starredCount += accountMessageCount.starred
+        }
+
+        return MessageCounts(unreadCount, starredCount)
+    }
+
+    override fun getUnreadMessageCount(account: Account, folderId: Long): Int {
+        return try {
+            val messageStore = messageStoreManager.getMessageStore(account)
+            return if (folderId == account.outboxFolderId) {
+                messageStore.getMessageCount(folderId)
+            } else {
+                messageStore.getUnreadMessageCount(folderId)
+            }
+        } catch (e: Exception) {
+            Timber.e(e, "Unable to getUnreadMessageCount for account: %s, folder: %d", account, folderId)
+            0
+        }
+    }
+
+    private fun getMessageCounts(account: Account, conditions: ConditionsTreeNode?): MessageCounts {
+        return try {
+            val messageStore = messageStoreManager.getMessageStore(account)
+            return MessageCounts(
+                unread = messageStore.getUnreadMessageCount(conditions),
+                starred = messageStore.getStarredMessageCount(conditions)
+            )
+        } catch (e: Exception) {
+            Timber.e(e, "Unable to getMessageCounts for account: %s", account)
+            MessageCounts(unread = 0, starred = 0)
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MessageReference.kt

@@ -0,0 +1,52 @@
+package com.fsck.k9.controller
+
+import com.fsck.k9.mail.filter.Base64
+import java.util.StringTokenizer
+
+data class MessageReference(
+    val accountUuid: String,
+    val folderId: Long,
+    val uid: String
+) {
+    fun toIdentityString(): String {
+        return buildString {
+            append(IDENTITY_VERSION_2)
+            append(IDENTITY_SEPARATOR)
+            append(Base64.encode(accountUuid))
+            append(IDENTITY_SEPARATOR)
+            append(Base64.encode(folderId.toString()))
+            append(IDENTITY_SEPARATOR)
+            append(Base64.encode(uid))
+        }
+    }
+
+    fun equals(accountUuid: String, folderId: Long, uid: String): Boolean {
+        return this.accountUuid == accountUuid && this.folderId == folderId && this.uid == uid
+    }
+
+    fun withModifiedUid(newUid: String): MessageReference {
+        return copy(uid = newUid)
+    }
+
+    companion object {
+        private const val IDENTITY_VERSION_2 = '#'
+        private const val IDENTITY_SEPARATOR = ":"
+
+        @JvmStatic
+        fun parse(identity: String?): MessageReference? {
+            if (identity == null || identity.isEmpty() || identity[0] != IDENTITY_VERSION_2) {
+                return null
+            }
+
+            val tokens = StringTokenizer(identity.substring(2), IDENTITY_SEPARATOR, false)
+            if (tokens.countTokens() < 3) {
+                return null
+            }
+
+            val accountUuid = Base64.decode(tokens.nextToken())
+            val folderId = Base64.decode(tokens.nextToken()).toLong()
+            val uid = Base64.decode(tokens.nextToken())
+            return MessageReference(accountUuid, folderId, uid)
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MessageReferenceHelper.java

@@ -0,0 +1,34 @@
+package com.fsck.k9.controller;
+
+
+import java.util.ArrayList;
+import java.util.List;
+
+import timber.log.Timber;
+
+
+public class MessageReferenceHelper {
+    public static List<MessageReference> toMessageReferenceList(List<String> messageReferenceStrings) {
+        List<MessageReference> messageReferences = new ArrayList<>(messageReferenceStrings.size());
+        for (String messageReferenceString : messageReferenceStrings) {
+            MessageReference messageReference = MessageReference.parse(messageReferenceString);
+            if (messageReference != null) {
+                messageReferences.add(messageReference);
+            } else {
+                Timber.w("Invalid message reference: %s", messageReferenceString);
+            }
+        }
+
+        return messageReferences;
+    }
+
+    public static ArrayList<String> toMessageReferenceStringList(List<MessageReference> messageReferences) {
+        ArrayList<String> messageReferenceStrings = new ArrayList<>(messageReferences.size());
+        for (MessageReference messageReference : messageReferences) {
+            String messageReferenceString = messageReference.toIdentityString();
+            messageReferenceStrings.add(messageReferenceString);
+        }
+
+        return messageReferenceStrings;
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MessagingControllerCommands.java

@@ -0,0 +1,269 @@
+package com.fsck.k9.controller;
+
+
+import java.util.List;
+import java.util.Map;
+
+import com.fsck.k9.Account;
+import com.fsck.k9.mail.Flag;
+import com.fsck.k9.mail.MessagingException;
+
+import static com.fsck.k9.controller.Preconditions.requireNotNull;
+import static com.fsck.k9.controller.Preconditions.requireValidUids;
+
+
+public class MessagingControllerCommands {
+    static final String COMMAND_APPEND = "append";
+    static final String COMMAND_REPLACE = "replace";
+    static final String COMMAND_MARK_ALL_AS_READ = "mark_all_as_read";
+    static final String COMMAND_SET_FLAG = "set_flag";
+    static final String COMMAND_DELETE = "delete";
+    static final String COMMAND_EXPUNGE = "expunge";
+    static final String COMMAND_MOVE_OR_COPY = "move_or_copy";
+    static final String COMMAND_MOVE_AND_MARK_AS_READ = "move_and_mark_as_read";
+    static final String COMMAND_EMPTY_TRASH = "empty_trash";
+
+    public abstract static class PendingCommand {
+        public long databaseId;
+
+
+        PendingCommand() { }
+
+        public abstract String getCommandName();
+        public abstract void execute(MessagingController controller, Account account) throws MessagingException;
+    }
+
+    public static class PendingMoveOrCopy extends PendingCommand {
+        public final long srcFolderId;
+        public final long destFolderId;
+        public final boolean isCopy;
+        public final List<String> uids;
+        public final Map<String, String> newUidMap;
+
+
+        public static PendingMoveOrCopy create(long srcFolderId, long destFolderId, boolean isCopy,
+                Map<String, String> uidMap) {
+            requireValidUids(uidMap);
+            return new PendingMoveOrCopy(srcFolderId, destFolderId, isCopy, null, uidMap);
+        }
+
+        private PendingMoveOrCopy(long srcFolderId, long destFolderId, boolean isCopy, List<String> uids,
+                Map<String, String> newUidMap) {
+            this.srcFolderId = srcFolderId;
+            this.destFolderId = destFolderId;
+            this.isCopy = isCopy;
+            this.uids = uids;
+            this.newUidMap = newUidMap;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_MOVE_OR_COPY;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingMoveOrCopy(this, account);
+        }
+    }
+
+    public static class PendingMoveAndMarkAsRead extends PendingCommand {
+        public final long srcFolderId;
+        public final long destFolderId;
+        public final Map<String, String> newUidMap;
+
+
+        public static PendingMoveAndMarkAsRead create(long srcFolderId, long destFolderId, Map<String, String> uidMap) {
+            requireValidUids(uidMap);
+            return new PendingMoveAndMarkAsRead(srcFolderId, destFolderId, uidMap);
+        }
+
+        private PendingMoveAndMarkAsRead(long srcFolderId, long destFolderId, Map<String, String> newUidMap) {
+            this.srcFolderId = srcFolderId;
+            this.destFolderId = destFolderId;
+            this.newUidMap = newUidMap;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_MOVE_AND_MARK_AS_READ;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingMoveAndRead(this, account);
+        }
+    }
+
+    public static class PendingEmptyTrash extends PendingCommand {
+        public static PendingEmptyTrash create() {
+            return new PendingEmptyTrash();
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_EMPTY_TRASH;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingEmptyTrash(account);
+        }
+    }
+
+    public static class PendingSetFlag extends PendingCommand {
+        public final long folderId;
+        public final boolean newState;
+        public final Flag flag;
+        public final List<String> uids;
+
+
+        public static PendingSetFlag create(long folderId, boolean newState, Flag flag, List<String> uids) {
+            requireNotNull(flag);
+            requireValidUids(uids);
+            return new PendingSetFlag(folderId, newState, flag, uids);
+        }
+
+        private PendingSetFlag(long folderId, boolean newState, Flag flag, List<String> uids) {
+            this.folderId = folderId;
+            this.newState = newState;
+            this.flag = flag;
+            this.uids = uids;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_SET_FLAG;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingSetFlag(this, account);
+        }
+    }
+
+    public static class PendingAppend extends PendingCommand {
+        public final long folderId;
+        public final String uid;
+
+
+        public static PendingAppend create(long folderId, String uid) {
+            requireNotNull(uid);
+            return new PendingAppend(folderId, uid);
+        }
+
+        private PendingAppend(long folderId, String uid) {
+            this.folderId = folderId;
+            this.uid = uid;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_APPEND;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingAppend(this, account);
+        }
+    }
+
+    public static class PendingReplace extends PendingCommand {
+        public final long folderId;
+        public final long uploadMessageId;
+        public final long deleteMessageId;
+
+
+        public static PendingReplace create(long folderId, long uploadMessageId, long deleteMessageId) {
+            return new PendingReplace(folderId, uploadMessageId, deleteMessageId);
+        }
+
+        private PendingReplace(long folderId, long uploadMessageId, long deleteMessageId) {
+            this.folderId = folderId;
+            this.uploadMessageId = uploadMessageId;
+            this.deleteMessageId = deleteMessageId;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_REPLACE;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingReplace(this, account);
+        }
+    }
+
+    public static class PendingMarkAllAsRead extends PendingCommand {
+        public final long folderId;
+
+
+        public static PendingMarkAllAsRead create(long folderId) {
+            return new PendingMarkAllAsRead(folderId);
+        }
+
+        private PendingMarkAllAsRead(long folderId) {
+            this.folderId = folderId;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_MARK_ALL_AS_READ;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingMarkAllAsRead(this, account);
+        }
+    }
+
+    public static class PendingDelete extends PendingCommand {
+        public final long folderId;
+        public final List<String> uids;
+
+
+        public static PendingDelete create(long folderId, List<String> uids) {
+            requireValidUids(uids);
+            return new PendingDelete(folderId, uids);
+        }
+
+        private PendingDelete(long folderId, List<String> uids) {
+            this.folderId = folderId;
+            this.uids = uids;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_DELETE;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingDelete(this, account);
+        }
+    }
+
+    public static class PendingExpunge extends PendingCommand {
+        public final long folderId;
+
+
+        public static PendingExpunge create(long folderId) {
+            return new PendingExpunge(folderId);
+        }
+
+        private PendingExpunge(long folderId) {
+            this.folderId = folderId;
+        }
+
+        @Override
+        public String getCommandName() {
+            return COMMAND_EXPUNGE;
+        }
+
+        @Override
+        public void execute(MessagingController controller, Account account) throws MessagingException {
+            controller.processPendingExpunge(this, account);
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/MessagingListener.java

@@ -0,0 +1,48 @@
+
+package com.fsck.k9.controller;
+
+
+import java.util.List;
+
+import android.content.Context;
+
+import com.fsck.k9.Account;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.Part;
+import com.fsck.k9.mailstore.LocalMessage;
+
+
+public interface MessagingListener {
+    void synchronizeMailboxStarted(Account account, long folderId);
+    void synchronizeMailboxHeadersStarted(Account account, String folderServerId);
+    void synchronizeMailboxHeadersProgress(Account account, String folderServerId, int completed, int total);
+    void synchronizeMailboxHeadersFinished(Account account, String folderServerId, int totalMessagesInMailbox,
+            int numNewMessages);
+    void synchronizeMailboxProgress(Account account, long folderId, int completed, int total);
+    void synchronizeMailboxNewMessage(Account account, String folderServerId, Message message);
+    void synchronizeMailboxRemovedMessage(Account account, String folderServerId, String messageServerId);
+    void synchronizeMailboxFinished(Account account, long folderId);
+    void synchronizeMailboxFailed(Account account, long folderId, String message);
+
+    void loadMessageRemoteFinished(Account account, long folderId, String uid);
+    void loadMessageRemoteFailed(Account account, long folderId, String uid, Throwable t);
+
+    void checkMailStarted(Context context, Account account);
+    void checkMailFinished(Context context, Account account);
+
+    void folderStatusChanged(Account account, long folderId);
+
+    void messageUidChanged(Account account, long folderId, String oldUid, String newUid);
+
+    void loadAttachmentFinished(Account account, Message message, Part part);
+    void loadAttachmentFailed(Account account, Message message, Part part, String reason);
+
+    void remoteSearchStarted(long folderId);
+    void remoteSearchServerQueryComplete(long folderId, int numResults, int maxResults);
+    void remoteSearchFinished(long folderId, int numResults, int maxResults, List<String> extraResults);
+    void remoteSearchFailed(String folderServerId, String err);
+
+    void enableProgressIndicator(boolean enable);
+
+    void updateProgress(int progress);
+}

app/core/src/main/java/com/fsck/k9/controller/NotificationOperations.kt

@@ -0,0 +1,63 @@
+package com.fsck.k9.controller
+
+import com.fsck.k9.Account
+import com.fsck.k9.Preferences
+import com.fsck.k9.mailstore.MessageStoreManager
+import com.fsck.k9.notification.NotificationController
+import com.fsck.k9.search.LocalSearch
+import com.fsck.k9.search.isNewMessages
+import com.fsck.k9.search.isSingleFolder
+import com.fsck.k9.search.isUnifiedInbox
+
+internal class NotificationOperations(
+    private val notificationController: NotificationController,
+    private val preferences: Preferences,
+    private val messageStoreManager: MessageStoreManager
+) {
+    fun clearNotifications(search: LocalSearch) {
+        if (search.isUnifiedInbox) {
+            clearUnifiedInboxNotifications()
+        } else if (search.isNewMessages) {
+            clearAllNotifications()
+        } else if (search.isSingleFolder) {
+            val account = search.firstAccount() ?: return
+            val folderId = search.folderIds.first()
+            clearNotifications(account, folderId)
+        } else {
+            // TODO: Remove notifications when updating the message list. That way we can easily remove only
+            //  notifications for messages that are currently displayed in the list.
+        }
+    }
+
+    private fun clearUnifiedInboxNotifications() {
+        for (account in preferences.accounts) {
+            val messageStore = messageStoreManager.getMessageStore(account)
+
+            val folderIds = messageStore.getFolders(excludeLocalOnly = true) { folderDetails ->
+                if (folderDetails.isIntegrate) folderDetails.id else null
+            }.filterNotNull().toSet()
+
+            if (folderIds.isNotEmpty()) {
+                notificationController.clearNewMailNotifications(account) { messageReferences ->
+                    messageReferences.filter { messageReference -> messageReference.folderId in folderIds }
+                }
+            }
+        }
+    }
+
+    private fun clearAllNotifications() {
+        for (account in preferences.accounts) {
+            notificationController.clearNewMailNotifications(account, clearNewMessageState = false)
+        }
+    }
+
+    private fun clearNotifications(account: Account, folderId: Long) {
+        notificationController.clearNewMailNotifications(account) { messageReferences ->
+            messageReferences.filter { messageReference -> messageReference.folderId == folderId }
+        }
+    }
+
+    private fun LocalSearch.firstAccount(): Account? {
+        return preferences.getAccount(accountUuids.first())
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/NotificationState.kt

@@ -0,0 +1,6 @@
+package com.fsck.k9.controller
+
+class NotificationState {
+    @get:JvmName("wasNotified")
+    var wasNotified: Boolean = false
+}

app/core/src/main/java/com/fsck/k9/controller/PendingCommandSerializer.java

@@ -0,0 +1,77 @@
+package com.fsck.k9.controller;
+
+
+import java.io.IOError;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import com.fsck.k9.controller.MessagingControllerCommands.PendingAppend;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingCommand;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingDelete;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingEmptyTrash;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingExpunge;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingMarkAllAsRead;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingMoveAndMarkAsRead;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingMoveOrCopy;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingReplace;
+import com.fsck.k9.controller.MessagingControllerCommands.PendingSetFlag;
+import com.squareup.moshi.JsonAdapter;
+import com.squareup.moshi.Moshi;
+
+
+public class PendingCommandSerializer {
+    private static final PendingCommandSerializer INSTANCE = new PendingCommandSerializer();
+
+
+    private final Map<String, JsonAdapter<? extends PendingCommand>> adapters;
+
+
+    private PendingCommandSerializer() {
+        Moshi moshi = new Moshi.Builder().build();
+        HashMap<String, JsonAdapter<? extends PendingCommand>> adapters = new HashMap<>();
+
+        adapters.put(MessagingControllerCommands.COMMAND_MOVE_OR_COPY, moshi.adapter(PendingMoveOrCopy.class));
+        adapters.put(MessagingControllerCommands.COMMAND_MOVE_AND_MARK_AS_READ,
+                moshi.adapter(PendingMoveAndMarkAsRead.class));
+        adapters.put(MessagingControllerCommands.COMMAND_APPEND, moshi.adapter(PendingAppend.class));
+        adapters.put(MessagingControllerCommands.COMMAND_REPLACE, moshi.adapter(PendingReplace.class));
+        adapters.put(MessagingControllerCommands.COMMAND_EMPTY_TRASH, moshi.adapter(PendingEmptyTrash.class));
+        adapters.put(MessagingControllerCommands.COMMAND_EXPUNGE, moshi.adapter(PendingExpunge.class));
+        adapters.put(MessagingControllerCommands.COMMAND_MARK_ALL_AS_READ, moshi.adapter(PendingMarkAllAsRead.class));
+        adapters.put(MessagingControllerCommands.COMMAND_SET_FLAG, moshi.adapter(PendingSetFlag.class));
+        adapters.put(MessagingControllerCommands.COMMAND_DELETE, moshi.adapter(PendingDelete.class));
+
+        this.adapters = Collections.unmodifiableMap(adapters);
+    }
+
+
+    public static PendingCommandSerializer getInstance() {
+        return INSTANCE;
+    }
+
+
+    public <T extends PendingCommand> String serialize(T command) {
+        // noinspection unchecked, we know the map has correctly matching adapters
+        JsonAdapter<T> adapter = (JsonAdapter<T>) adapters.get(command.getCommandName());
+        if (adapter == null) {
+            throw new IllegalArgumentException("Unsupported pending command type!");
+        }
+        return adapter.toJson(command);
+    }
+
+    public PendingCommand unserialize(long databaseId, String commandName, String data) {
+        JsonAdapter<? extends PendingCommand> adapter = adapters.get(commandName);
+        if (adapter == null) {
+            throw new IllegalArgumentException("Unsupported pending command type!");
+        }
+        try {
+            PendingCommand command = adapter.fromJson(data);
+            command.databaseId = databaseId;
+            return command;
+        } catch (IOException e) {
+            throw new IOError(e);
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/Preconditions.kt

@@ -0,0 +1,29 @@
+@file:JvmName("Preconditions")
+
+package com.fsck.k9.controller
+
+import com.fsck.k9.K9
+
+fun <T : Any> requireNotNull(value: T?) {
+    kotlin.requireNotNull(value)
+}
+
+fun requireValidUids(uidMap: Map<String?, String?>?) {
+    kotlin.requireNotNull(uidMap)
+    for ((sourceUid, destinationUid) in uidMap) {
+        requireNotLocalUid(sourceUid)
+        kotlin.requireNotNull(destinationUid)
+    }
+}
+
+fun requireValidUids(uids: List<String?>?) {
+    kotlin.requireNotNull(uids)
+    for (uid in uids) {
+        requireNotLocalUid(uid)
+    }
+}
+
+private fun requireNotLocalUid(uid: String?) {
+    kotlin.requireNotNull(uid)
+    require(!uid.startsWith(K9.LOCAL_UID_PREFIX)) { "Local UID found: $uid" }
+}

app/core/src/main/java/com/fsck/k9/controller/ProgressBodyFactory.java

@@ -0,0 +1,42 @@
+package com.fsck.k9.controller;
+
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.Timer;
+import java.util.TimerTask;
+
+import com.fsck.k9.mail.DefaultBodyFactory;
+import org.apache.commons.io.output.CountingOutputStream;
+
+
+class ProgressBodyFactory extends DefaultBodyFactory {
+    private final ProgressListener progressListener;
+
+
+    ProgressBodyFactory(ProgressListener progressListener) {
+        this.progressListener = progressListener;
+    }
+
+    @Override
+    protected void copyData(InputStream inputStream, OutputStream outputStream) throws IOException {
+        Timer timer = new Timer();
+        try (CountingOutputStream countingOutputStream = new CountingOutputStream(outputStream)) {
+            timer.scheduleAtFixedRate(new TimerTask() {
+                @Override
+                public void run() {
+                    progressListener.updateProgress(countingOutputStream.getCount());
+                }
+            }, 0, 50);
+
+            super.copyData(inputStream, countingOutputStream);
+        } finally {
+            timer.cancel();
+        }
+    }
+
+    interface ProgressListener {
+        void updateProgress(int progress);
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/SimpleMessagingListener.java

@@ -0,0 +1,108 @@
+
+package com.fsck.k9.controller;
+
+
+import java.util.List;
+
+import android.content.Context;
+
+import com.fsck.k9.Account;
+import com.fsck.k9.mail.Message;
+import com.fsck.k9.mail.Part;
+
+
+public abstract class SimpleMessagingListener implements MessagingListener {
+    @Override
+    public void synchronizeMailboxStarted(Account account, long folderId) {
+    }
+
+    @Override
+    public void synchronizeMailboxHeadersStarted(Account account, String folderServerId) {
+    }
+
+    @Override
+    public void synchronizeMailboxHeadersProgress(Account account, String folderServerId, int completed, int total) {
+    }
+
+    @Override
+    public void synchronizeMailboxHeadersFinished(Account account, String folderServerId, int totalMessagesInMailbox,
+            int numNewMessages) {
+    }
+
+    @Override
+    public void synchronizeMailboxProgress(Account account, long folderId, int completed, int total) {
+    }
+
+    @Override
+    public void synchronizeMailboxNewMessage(Account account, String folderServerId, Message message) {
+    }
+
+    @Override
+    public void synchronizeMailboxRemovedMessage(Account account, String folderServerId, String messageServerId) {
+    }
+
+    @Override
+    public void synchronizeMailboxFinished(Account account, long folderId) {
+    }
+
+    @Override
+    public void synchronizeMailboxFailed(Account account, long folderId, String message) {
+    }
+
+    @Override
+    public void loadMessageRemoteFinished(Account account, long folderId, String uid) {
+    }
+
+    @Override
+    public void loadMessageRemoteFailed(Account account, long folderId, String uid, Throwable t) {
+    }
+
+    @Override
+    public void checkMailStarted(Context context, Account account) {
+    }
+
+    @Override
+    public void checkMailFinished(Context context, Account account) {
+    }
+
+    @Override
+    public void folderStatusChanged(Account account, long folderId) {
+    }
+
+    @Override
+    public void messageUidChanged(Account account, long folderId, String oldUid, String newUid) {
+    }
+
+    @Override
+    public void loadAttachmentFinished(Account account, Message message, Part part) {
+    }
+
+    @Override
+    public void loadAttachmentFailed(Account account, Message message, Part part, String reason) {
+    }
+
+    @Override
+    public void remoteSearchStarted(long folderId) {
+    }
+
+    @Override
+    public void remoteSearchServerQueryComplete(long folderId, int numResults, int maxResults) {
+    }
+
+    @Override
+    public void remoteSearchFinished(long folderId, int numResults, int maxResults, List<String> extraResults) {
+    }
+
+    @Override
+    public void remoteSearchFailed(String folderServerId, String err) {
+    }
+
+    @Override
+    public void enableProgressIndicator(boolean enable) {
+    }
+
+    @Override
+    public void updateProgress(int progress) {
+
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/UidReverseComparator.java

@@ -0,0 +1,34 @@
+package com.fsck.k9.controller;
+
+
+import java.util.Comparator;
+
+import com.fsck.k9.mail.Message;
+
+
+public class UidReverseComparator implements Comparator<Message> {
+    @Override
+    public int compare(Message messageLeft, Message messageRight) {
+        Long uidLeft = getUidForMessage(messageLeft);
+        Long uidRight = getUidForMessage(messageRight);
+
+        if (uidLeft == null && uidRight == null) {
+            return 0;
+        } else if (uidLeft == null) {
+            return 1;
+        } else if (uidRight == null) {
+            return -1;
+        }
+
+        // reverse order
+        return uidRight.compareTo(uidLeft);
+    }
+
+    private Long getUidForMessage(Message message) {
+        try {
+            return Long.parseLong(message.getUid());
+        } catch (NullPointerException | NumberFormatException e) {
+            return null;
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/AccountPushController.kt

@@ -0,0 +1,103 @@
+package com.fsck.k9.controller.push
+
+import com.fsck.k9.Account
+import com.fsck.k9.Account.FolderMode
+import com.fsck.k9.Preferences
+import com.fsck.k9.backend.BackendManager
+import com.fsck.k9.backend.api.BackendPusher
+import com.fsck.k9.backend.api.BackendPusherCallback
+import com.fsck.k9.controller.MessagingController
+import com.fsck.k9.mailstore.FolderRepository
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.launch
+import timber.log.Timber
+
+internal class AccountPushController(
+    private val backendManager: BackendManager,
+    private val messagingController: MessagingController,
+    private val preferences: Preferences,
+    private val folderRepository: FolderRepository,
+    backgroundDispatcher: CoroutineDispatcher = Dispatchers.IO,
+    private val account: Account
+) {
+    private val coroutineScope = CoroutineScope(backgroundDispatcher)
+
+    @Volatile
+    private var backendPusher: BackendPusher? = null
+
+    private val backendPusherCallback = object : BackendPusherCallback {
+        override fun onPushEvent(folderServerId: String) {
+            syncFolders(folderServerId)
+        }
+
+        override fun onPushError(exception: Exception) {
+            messagingController.handleException(account, exception)
+        }
+
+        override fun onPushNotSupported() {
+            Timber.v("AccountPushController(%s) - Push not supported. Disabling Push for account.", account.uuid)
+            disablePush()
+        }
+    }
+
+    fun start() {
+        Timber.v("AccountPushController(%s).start()", account.uuid)
+        startBackendPusher()
+        startListeningForPushFolders()
+    }
+
+    fun stop() {
+        Timber.v("AccountPushController(%s).stop()", account.uuid)
+        stopListeningForPushFolders()
+        stopBackendPusher()
+    }
+
+    fun reconnect() {
+        Timber.v("AccountPushController(%s).reconnect()", account.uuid)
+        backendPusher?.reconnect()
+    }
+
+    private fun startBackendPusher() {
+        val backend = backendManager.getBackend(account)
+        backendPusher = backend.createPusher(backendPusherCallback).also { backendPusher ->
+            backendPusher.start()
+        }
+    }
+
+    private fun stopBackendPusher() {
+        backendPusher?.stop()
+        backendPusher = null
+    }
+
+    private fun startListeningForPushFolders() {
+        coroutineScope.launch {
+            folderRepository.getPushFoldersFlow(account).collect { remoteFolders ->
+                val folderServerIds = remoteFolders.map { it.serverId }
+                updatePushFolders(folderServerIds)
+            }
+        }
+    }
+
+    private fun stopListeningForPushFolders() {
+        coroutineScope.cancel()
+    }
+
+    private fun updatePushFolders(folderServerIds: List<String>) {
+        Timber.v("AccountPushController(%s).updatePushFolders(): %s", account.uuid, folderServerIds)
+
+        backendPusher?.updateFolders(folderServerIds)
+    }
+
+    private fun syncFolders(folderServerId: String) {
+        messagingController.synchronizeMailboxBlocking(account, folderServerId)
+    }
+
+    private fun disablePush() {
+        account.folderPushMode = FolderMode.NONE
+        preferences.saveAccount(account)
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/AccountPushControllerFactory.kt

@@ -0,0 +1,24 @@
+package com.fsck.k9.controller.push
+
+import com.fsck.k9.Account
+import com.fsck.k9.Preferences
+import com.fsck.k9.backend.BackendManager
+import com.fsck.k9.controller.MessagingController
+import com.fsck.k9.mailstore.FolderRepository
+
+internal class AccountPushControllerFactory(
+    private val backendManager: BackendManager,
+    private val messagingController: MessagingController,
+    private val folderRepository: FolderRepository,
+    private val preferences: Preferences
+) {
+    fun create(account: Account): AccountPushController {
+        return AccountPushController(
+            backendManager,
+            messagingController,
+            preferences,
+            folderRepository,
+            account = account
+        )
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/AutoSyncManager.kt

@@ -0,0 +1,57 @@
+package com.fsck.k9.controller.push
+
+import android.content.BroadcastReceiver
+import android.content.ContentResolver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import com.fsck.k9.K9
+import timber.log.Timber
+
+/**
+ * Listen for changes to the system's auto sync setting.
+ */
+internal class AutoSyncManager(private val context: Context) {
+    val isAutoSyncDisabled: Boolean
+        get() = respectSystemAutoSync && !ContentResolver.getMasterSyncAutomatically()
+
+    val respectSystemAutoSync: Boolean
+        get() = K9.backgroundOps == K9.BACKGROUND_OPS.WHEN_CHECKED_AUTO_SYNC
+
+    private var isRegistered = false
+    private var listener: AutoSyncListener? = null
+
+    private val intentFilter = IntentFilter().apply {
+        addAction("com.android.sync.SYNC_CONN_STATUS_CHANGED")
+    }
+
+    private val receiver = object : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent?) {
+            val listener = synchronized(this@AutoSyncManager) { listener }
+            listener?.onAutoSyncChanged()
+        }
+    }
+
+    @Synchronized
+    fun registerListener(listener: AutoSyncListener) {
+        if (!isRegistered) {
+            Timber.v("Registering auto sync listener")
+            isRegistered = true
+            this.listener = listener
+            context.registerReceiver(receiver, intentFilter)
+        }
+    }
+
+    @Synchronized
+    fun unregisterListener() {
+        if (isRegistered) {
+            Timber.v("Unregistering auto sync listener")
+            isRegistered = false
+            context.unregisterReceiver(receiver)
+        }
+    }
+}
+
+internal fun interface AutoSyncListener {
+    fun onAutoSyncChanged()
+}

app/core/src/main/java/com/fsck/k9/controller/push/BootCompleteReceiver.kt

@@ -0,0 +1,46 @@
+package com.fsck.k9.controller.push
+
+import android.content.BroadcastReceiver
+import android.content.ComponentName
+import android.content.Context
+import android.content.Intent
+import android.content.pm.PackageManager.COMPONENT_ENABLED_STATE_DISABLED
+import android.content.pm.PackageManager.COMPONENT_ENABLED_STATE_ENABLED
+import android.content.pm.PackageManager.DONT_KILL_APP
+import java.lang.Exception
+import org.koin.core.component.KoinComponent
+import org.koin.core.component.inject
+import timber.log.Timber
+
+class BootCompleteReceiver : BroadcastReceiver(), KoinComponent {
+    private val pushController: PushController by inject()
+
+    override fun onReceive(context: Context, intent: Intent?) {
+        Timber.v("BootCompleteReceiver.onReceive()")
+
+        pushController.init()
+    }
+}
+
+class BootCompleteManager(context: Context) {
+    private val packageManager = context.packageManager
+    private val componentName = ComponentName(context, BootCompleteReceiver::class.java)
+
+    fun enableReceiver() {
+        Timber.v("Enable BootCompleteReceiver")
+        try {
+            packageManager.setComponentEnabledSetting(componentName, COMPONENT_ENABLED_STATE_ENABLED, DONT_KILL_APP)
+        } catch (e: Exception) {
+            Timber.e(e, "Error enabling BootCompleteReceiver")
+        }
+    }
+
+    fun disableReceiver() {
+        Timber.v("Disable BootCompleteReceiver")
+        try {
+            packageManager.setComponentEnabledSetting(componentName, COMPONENT_ENABLED_STATE_DISABLED, DONT_KILL_APP)
+        } catch (e: Exception) {
+            Timber.e(e, "Error disabling BootCompleteReceiver")
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/KoinModule.kt

@@ -0,0 +1,30 @@
+package com.fsck.k9.controller.push
+
+import org.koin.dsl.module
+
+internal val controllerPushModule = module {
+    single { PushServiceManager(context = get()) }
+    single { BootCompleteManager(context = get()) }
+    single { AutoSyncManager(context = get()) }
+    single {
+        AccountPushControllerFactory(
+            backendManager = get(),
+            messagingController = get(),
+            folderRepository = get(),
+            preferences = get()
+        )
+    }
+    single {
+        PushController(
+            preferences = get(),
+            generalSettingsManager = get(),
+            backendManager = get(),
+            pushServiceManager = get(),
+            bootCompleteManager = get(),
+            autoSyncManager = get(),
+            pushNotificationManager = get(),
+            connectivityManager = get(),
+            accountPushControllerFactory = get()
+        )
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/PushController.kt

@@ -0,0 +1,252 @@
+package com.fsck.k9.controller.push
+
+import com.fsck.k9.Account
+import com.fsck.k9.Account.FolderMode
+import com.fsck.k9.Preferences
+import com.fsck.k9.backend.BackendManager
+import com.fsck.k9.network.ConnectivityChangeListener
+import com.fsck.k9.network.ConnectivityManager
+import com.fsck.k9.notification.PushNotificationManager
+import com.fsck.k9.notification.PushNotificationState
+import com.fsck.k9.notification.PushNotificationState.LISTENING
+import com.fsck.k9.notification.PushNotificationState.WAIT_BACKGROUND_SYNC
+import com.fsck.k9.notification.PushNotificationState.WAIT_NETWORK
+import com.fsck.k9.preferences.BackgroundSync
+import com.fsck.k9.preferences.GeneralSettingsManager
+import java.util.concurrent.Executors
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.asCoroutineDispatcher
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.launch
+import timber.log.Timber
+
+/**
+ * Starts and stops [AccountPushController]s as necessary. Manages the Push foreground service.
+ */
+class PushController internal constructor(
+    private val preferences: Preferences,
+    private val generalSettingsManager: GeneralSettingsManager,
+    private val backendManager: BackendManager,
+    private val pushServiceManager: PushServiceManager,
+    private val bootCompleteManager: BootCompleteManager,
+    private val autoSyncManager: AutoSyncManager,
+    private val pushNotificationManager: PushNotificationManager,
+    private val connectivityManager: ConnectivityManager,
+    private val accountPushControllerFactory: AccountPushControllerFactory,
+    private val coroutineScope: CoroutineScope = GlobalScope,
+    private val coroutineDispatcher: CoroutineDispatcher = Executors.newSingleThreadExecutor().asCoroutineDispatcher()
+) {
+    private val lock = Any()
+    private var initializationStarted = false
+    private val pushers = mutableMapOf<String, AccountPushController>()
+
+    private val autoSyncListener = AutoSyncListener(::onAutoSyncChanged)
+    private val connectivityChangeListener = object : ConnectivityChangeListener {
+        override fun onConnectivityChanged() = this@PushController.onConnectivityChanged()
+        override fun onConnectivityLost() = this@PushController.onConnectivityLost()
+    }
+
+    /**
+     * Initialize [PushController].
+     *
+     * Only call this method in situations where starting a foreground service is allowed.
+     * See https://developer.android.com/about/versions/12/foreground-services
+     */
+    fun init() {
+        synchronized(lock) {
+            if (initializationStarted) {
+                return
+            }
+            initializationStarted = true
+        }
+
+        coroutineScope.launch(coroutineDispatcher) {
+            initInBackground()
+        }
+    }
+
+    fun disablePush() {
+        Timber.v("PushController.disablePush()")
+
+        coroutineScope.launch(coroutineDispatcher) {
+            for (account in preferences.accounts) {
+                account.folderPushMode = FolderMode.NONE
+                preferences.saveAccount(account)
+            }
+        }
+    }
+
+    private fun initInBackground() {
+        Timber.v("PushController.initInBackground()")
+
+        preferences.addOnAccountsChangeListener(::onAccountsChanged)
+        listenForBackgroundSyncChanges()
+        backendManager.addListener(::onBackendChanged)
+
+        updatePushers()
+    }
+
+    private fun listenForBackgroundSyncChanges() {
+        generalSettingsManager.getSettingsFlow()
+            .map { it.backgroundSync }
+            .distinctUntilChanged()
+            .onEach {
+                launchUpdatePushers()
+            }
+            .launchIn(coroutineScope)
+    }
+
+    private fun onAccountsChanged() {
+        launchUpdatePushers()
+    }
+
+    private fun onAutoSyncChanged() {
+        launchUpdatePushers()
+    }
+
+    private fun onConnectivityChanged() {
+        coroutineScope.launch(coroutineDispatcher) {
+            synchronized(lock) {
+                for (accountPushController in pushers.values) {
+                    accountPushController.reconnect()
+                }
+            }
+
+            updatePushers()
+        }
+    }
+
+    private fun onConnectivityLost() {
+        launchUpdatePushers()
+    }
+
+    private fun onBackendChanged(account: Account) {
+        coroutineScope.launch(coroutineDispatcher) {
+            val accountPushController = synchronized(lock) {
+                pushers.remove(account.uuid)
+            }
+
+            accountPushController?.stop()
+            updatePushers()
+        }
+    }
+
+    private fun launchUpdatePushers() {
+        coroutineScope.launch(coroutineDispatcher) {
+            updatePushers()
+        }
+    }
+
+    private fun updatePushers() {
+        Timber.v("PushController.updatePushers()")
+
+        val generalSettings = generalSettingsManager.getSettings()
+
+        val backgroundSyncDisabledViaSystem = autoSyncManager.isAutoSyncDisabled
+        val backgroundSyncDisabledInApp = generalSettings.backgroundSync == BackgroundSync.NEVER
+        val networkNotAvailable = !connectivityManager.isNetworkAvailable()
+        val realPushAccounts = getPushAccounts()
+
+        val pushAccounts = if (backgroundSyncDisabledViaSystem || backgroundSyncDisabledInApp || networkNotAvailable) {
+            emptyList()
+        } else {
+            realPushAccounts
+        }
+        val pushAccountUuids = pushAccounts.map { it.uuid }
+
+        val arePushersActive = synchronized(lock) {
+            val currentPushAccountUuids = pushers.keys
+            val startPushAccountUuids = pushAccountUuids - currentPushAccountUuids
+            val stopPushAccountUuids = currentPushAccountUuids - pushAccountUuids
+
+            if (stopPushAccountUuids.isNotEmpty()) {
+                Timber.v("..Stopping PushController for accounts: %s", stopPushAccountUuids)
+                for (accountUuid in stopPushAccountUuids) {
+                    val accountPushController = pushers.remove(accountUuid)
+                    accountPushController?.stop()
+                }
+            }
+
+            if (startPushAccountUuids.isNotEmpty()) {
+                Timber.v("..Starting PushController for accounts: %s", startPushAccountUuids)
+                for (accountUuid in startPushAccountUuids) {
+                    val account = preferences.getAccount(accountUuid) ?: error("Account not found: $accountUuid")
+                    pushers[accountUuid] = accountPushControllerFactory.create(account).also { accountPushController ->
+                        accountPushController.start()
+                    }
+                }
+            }
+
+            Timber.v("..Running PushControllers: %s", pushers.keys)
+
+            pushers.isNotEmpty()
+        }
+
+        when {
+            realPushAccounts.isEmpty() -> {
+                stopServices()
+            }
+            backgroundSyncDisabledViaSystem -> {
+                setPushNotificationState(WAIT_BACKGROUND_SYNC)
+                startServices()
+            }
+            networkNotAvailable -> {
+                setPushNotificationState(WAIT_NETWORK)
+                startServices()
+            }
+            arePushersActive -> {
+                setPushNotificationState(LISTENING)
+                startServices()
+            }
+            else -> {
+                stopServices()
+            }
+        }
+    }
+
+    private fun getPushAccounts(): List<Account> {
+        return preferences.accounts.filter { account ->
+            account.folderPushMode != FolderMode.NONE && backendManager.getBackend(account).isPushCapable
+        }
+    }
+    private fun setPushNotificationState(notificationState: PushNotificationState) {
+        pushNotificationManager.notificationState = notificationState
+    }
+
+    private fun startServices() {
+        pushServiceManager.start()
+        bootCompleteManager.enableReceiver()
+        registerAutoSyncListener()
+        registerConnectivityChangeListener()
+        connectivityManager.start()
+    }
+
+    private fun stopServices() {
+        pushServiceManager.stop()
+        bootCompleteManager.disableReceiver()
+        autoSyncManager.unregisterListener()
+        unregisterConnectivityChangeListener()
+        connectivityManager.stop()
+    }
+
+    private fun registerAutoSyncListener() {
+        if (autoSyncManager.respectSystemAutoSync) {
+            autoSyncManager.registerListener(autoSyncListener)
+        } else {
+            autoSyncManager.unregisterListener()
+        }
+    }
+
+    private fun registerConnectivityChangeListener() {
+        connectivityManager.addListener(connectivityChangeListener)
+    }
+
+    private fun unregisterConnectivityChangeListener() {
+        connectivityManager.removeListener(connectivityChangeListener)
+    }
+}

app/core/src/main/java/com/fsck/k9/controller/push/PushService.kt

@@ -0,0 +1,58 @@
+package com.fsck.k9.controller.push
+
+import android.app.Service
+import android.content.Intent
+import android.content.pm.ServiceInfo
+import android.os.Build
+import android.os.IBinder
+import com.fsck.k9.notification.PushNotificationManager
+import org.koin.android.ext.android.inject
+import timber.log.Timber
+
+/**
+ * Foreground service that is used to keep the app alive while listening for new emails (Push).
+ */
+class PushService : Service() {
+    private val pushNotificationManager: PushNotificationManager by inject()
+    private val pushController: PushController by inject()
+
+    override fun onCreate() {
+        Timber.v("PushService.onCreate()")
+        super.onCreate()
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        Timber.v("PushService.onStartCommand()")
+        super.onStartCommand(intent, flags, startId)
+
+        startForeground()
+        initializePushController()
+
+        return START_STICKY
+    }
+
+    override fun onDestroy() {
+        Timber.v("PushService.onDestroy()")
+        pushNotificationManager.setForegroundServiceStopped()
+        super.onDestroy()
+    }
+
+    private fun startForeground() {
+        val notificationId = pushNotificationManager.notificationId
+        val notification = pushNotificationManager.createForegroundNotification()
+
+        if (Build.VERSION.SDK_INT >= 29) {
+            startForeground(notificationId, notification, ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC)
+        } else {
+            startForeground(notificationId, notification)
+        }
+    }
+
+    private fun initializePushController() {
+        // When the app is killed by the system and later recreated to start this service nobody else is initializing
+        // PushController. So we'll have to do it here.
+        pushController.init()
+    }
+
+    override fun onBind(intent: Intent?): IBinder? = null
+}

app/core/src/main/java/com/fsck/k9/controller/push/PushServiceManager.kt

@@ -0,0 +1,54 @@
+package com.fsck.k9.controller.push
+
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import java.util.concurrent.atomic.AtomicBoolean
+import timber.log.Timber
+
+/**
+ * Manages starting and stopping [PushService].
+ */
+internal class PushServiceManager(private val context: Context) {
+    private var isServiceStarted = AtomicBoolean(false)
+
+    fun start() {
+        Timber.v("PushServiceManager.start()")
+        if (isServiceStarted.compareAndSet(false, true)) {
+            startService()
+        } else {
+            Timber.v("..PushService already running")
+        }
+    }
+
+    fun stop() {
+        Timber.v("PushServiceManager.stop()")
+        if (isServiceStarted.compareAndSet(true, false)) {
+            stopService()
+        } else {
+            Timber.v("..PushService is not running")
+        }
+    }
+
+    private fun startService() {
+        try {
+            val intent = Intent(context, PushService::class.java)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                context.startForegroundService(intent)
+            } else {
+                context.startService(intent)
+            }
+        } catch (e: Exception) {
+            Timber.e(e, "Exception while trying to start PushService")
+        }
+    }
+
+    private fun stopService() {
+        try {
+            val intent = Intent(context, PushService::class.java)
+            context.stopService(intent)
+        } catch (e: Exception) {
+            Timber.w(e, "Exception while trying to stop PushService")
+        }
+    }
+}

app/core/src/main/java/com/fsck/k9/crypto/EncryptionExtractor.kt

@@ -0,0 +1,17 @@
+package com.fsck.k9.crypto
+
+import android.content.ContentValues
+import com.fsck.k9.mail.Message
+import com.fsck.k9.message.extractors.PreviewResult
+
+interface EncryptionExtractor {
+    fun extractEncryption(message: Message): EncryptionResult?
+}
+
+data class EncryptionResult(
+    val encryptionType: String,
+    val attachmentCount: Int,
+    val previewResult: PreviewResult = PreviewResult.encrypted(),
+    val textForSearchIndex: String? = null,
+    val extraContentValues: ContentValues? = null
+)

app/core/src/main/java/com/fsck/k9/crypto/KoinModule.kt

@@ -0,0 +1,11 @@
+package com.fsck.k9.crypto
+
+import androidx.lifecycle.LifecycleOwner
+import org.koin.dsl.module
+import org.openintents.openpgp.OpenPgpApiManager
+
+val openPgpModule = module {
+    factory { (lifecycleOwner: LifecycleOwner) ->
+        OpenPgpApiManager(get(), lifecycleOwner)
+    }
+}

app/core/src/main/java/com/fsck/k9/crypto/MessageCryptoStructureDetector.java

@@ -0,0 +1,303 @@
+package com.fsck.k9.crypto;
+
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import com.fsck.k9.helper.StringHelper;
+import com.fsck.k9.mail.Body;
+import com.fsck.k9.mail.BodyPart;
+import com.fsck.k9.mail.MessagingException;
+import com.fsck.k9.mail.Multipart;
+import com.fsck.k9.mail.Part;
+import com.fsck.k9.mail.internet.MessageExtractor;
+import com.fsck.k9.mail.internet.MimeBodyPart;
+import com.fsck.k9.mail.internet.MimeMultipart;
+import com.fsck.k9.mail.internet.MimeUtility;
+import com.fsck.k9.mailstore.CryptoResultAnnotation;
+import com.fsck.k9.mailstore.MessageCryptoAnnotations;
+
+import static com.fsck.k9.mail.internet.MimeUtility.isSameMimeType;
+
+
+public class MessageCryptoStructureDetector {
+    private static final String MULTIPART_ENCRYPTED = "multipart/encrypted";
+    private static final String MULTIPART_SIGNED = "multipart/signed";
+    private static final String PROTOCOL_PARAMETER = "protocol";
+    private static final String APPLICATION_PGP_ENCRYPTED = "application/pgp-encrypted";
+    private static final String APPLICATION_PGP_SIGNATURE = "application/pgp-signature";
+    private static final String TEXT_PLAIN = "text/plain";
+    // APPLICATION/PGP is a special case which occurs from mutt. see http://www.mutt.org/doc/PGP-Notes.txt
+    private static final String APPLICATION_PGP = "application/pgp";
+
+    private static final String PGP_INLINE_START_MARKER = "-----BEGIN PGP MESSAGE-----";
+    private static final String PGP_INLINE_SIGNED_START_MARKER = "-----BEGIN PGP SIGNED MESSAGE-----";
+    private static final int TEXT_LENGTH_FOR_INLINE_CHECK = 36;
+
+
+    public static Part findPrimaryEncryptedOrSignedPart(Part part, List<Part> outputExtraParts) {
+        if (isPartEncryptedOrSigned(part)) {
+            return part;
+        }
+
+        Part foundPart;
+
+        foundPart = findPrimaryPartInAlternative(part);
+        if (foundPart != null) {
+            return foundPart;
+        }
+
+        foundPart = findPrimaryPartInMixed(part, outputExtraParts);
+        if (foundPart != null) {
+            return foundPart;
+        }
+
+        return null;
+    }
+
+    @Nullable
+    private static Part findPrimaryPartInMixed(Part part, List<Part> outputExtraParts) {
+        Body body = part.getBody();
+
+        boolean isMultipartMixed = part.isMimeType("multipart/mixed") && body instanceof Multipart;
+        if (!isMultipartMixed) {
+            return null;
+        }
+
+        Multipart multipart = (Multipart) body;
+        if (multipart.getCount() == 0) {
+            return null;
+        }
+        
+        BodyPart firstBodyPart = multipart.getBodyPart(0);
+
+        Part foundPart;
+        if (isPartEncryptedOrSigned(firstBodyPart)) {
+            foundPart = firstBodyPart;
+        } else {
+            foundPart = findPrimaryPartInAlternative(firstBodyPart);
+        }
+
+        if (foundPart != null && outputExtraParts != null) {
+            for (int i = 1; i < multipart.getCount(); i++) {
+                outputExtraParts.add(multipart.getBodyPart(i));
+            }
+        }
+
+        return foundPart;
+    }
+
+    private static Part findPrimaryPartInAlternative(Part part) {
+        Body body = part.getBody();
+        if (part.isMimeType("multipart/alternative") && body instanceof Multipart) {
+            Multipart multipart = (Multipart) body;
+            if (multipart.getCount() == 0) {
+                return null;
+            }
+            
+            BodyPart firstBodyPart = multipart.getBodyPart(0);
+            if (isPartPgpInlineEncryptedOrSigned(firstBodyPart)) {
+                return firstBodyPart;
+            }
+        }
+
+        return null;
+    }
+
+    public static List<Part> findMultipartEncryptedParts(Part startPart) {
+        List<Part> encryptedParts = new ArrayList<>();
+        Stack<Part> partsToCheck = new Stack<>();
+        partsToCheck.push(startPart);
+
+        while (!partsToCheck.isEmpty()) {
+            Part part = partsToCheck.pop();
+            Body body = part.getBody();
+
+            if (isPartMultipartEncrypted(part)) {
+                encryptedParts.add(part);
+                continue;
+            }
+
+            if (body instanceof Multipart) {
+                Multipart multipart = (Multipart) body;
+                for (int i = multipart.getCount() - 1; i >= 0; i--) {
+                    BodyPart bodyPart = multipart.getBodyPart(i);
+                    partsToCheck.push(bodyPart);
+                }
+            }
+        }
+
+        return encryptedParts;
+    }
+
+    public static List<Part> findMultipartSignedParts(Part startPart, MessageCryptoAnnotations messageCryptoAnnotations) {
+        List<Part> signedParts = new ArrayList<>();
+        Stack<Part> partsToCheck = new Stack<>();
+        partsToCheck.push(startPart);
+
+        while (!partsToCheck.isEmpty()) {
+            Part part = partsToCheck.pop();
+            if (messageCryptoAnnotations.has(part)) {
+                CryptoResultAnnotation resultAnnotation = messageCryptoAnnotations.get(part);
+                MimeBodyPart replacementData = resultAnnotation.getReplacementData();
+                if (replacementData != null) {
+                    part = replacementData;
+                }
+            }
+            Body body = part.getBody();
+
+            if (isPartMultipartSigned(part)) {
+                signedParts.add(part);
+                continue;
+            }
+
+            if (body instanceof Multipart) {
+                Multipart multipart = (Multipart) body;
+                for (int i = multipart.getCount() - 1; i >= 0; i--) {
+                    BodyPart bodyPart = multipart.getBodyPart(i);
+                    partsToCheck.push(bodyPart);
+                }
+            }
+        }
+
+        return signedParts;
+    }
+
+    public static List<Part> findPgpInlineParts(Part startPart) {
+        List<Part> inlineParts = new ArrayList<>();
+        Stack<Part> partsToCheck = new Stack<>();
+        partsToCheck.push(startPart);
+
+        while (!partsToCheck.isEmpty()) {
+            Part part = partsToCheck.pop();
+            Body body = part.getBody();
+
+            if (isPartPgpInlineEncryptedOrSigned(part)) {
+                inlineParts.add(part);
+                continue;
+            }
+
+            if (body instanceof Multipart) {
+                Multipart multipart = (Multipart) body;
+                for (int i = multipart.getCount() - 1; i >= 0; i--) {
+                    BodyPart bodyPart = multipart.getBodyPart(i);
+                    partsToCheck.push(bodyPart);
+                }
+            }
+        }
+
+        return inlineParts;
+    }
+
+    public static byte[] getSignatureData(Part part) throws IOException, MessagingException {
+        if (isPartMultipartSigned(part)) {
+            Body body = part.getBody();
+            if (body instanceof Multipart) {
+                Multipart multi = (Multipart) body;
+                BodyPart signatureBody = multi.getBodyPart(1);
+                ByteArrayOutputStream bos = new ByteArrayOutputStream();
+                signatureBody.getBody().writeTo(bos);
+                return bos.toByteArray();
+            }
+        }
+
+        return null;
+    }
+
+    private static boolean isPartEncryptedOrSigned(Part part) {
+        return isPartMultipartEncrypted(part) || isPartMultipartSigned(part) || isPartPgpInlineEncryptedOrSigned(part);
+    }
+
+    private static boolean isPartMultipartSigned(Part part) {
+        if (!isSameMimeType(part.getMimeType(), MULTIPART_SIGNED)) {
+            return false;
+        }
+        if (! (part.getBody() instanceof MimeMultipart)) {
+            return false;
+        }
+        MimeMultipart mimeMultipart = (MimeMultipart) part.getBody();
+        if (mimeMultipart.getCount() != 2) {
+            return false;
+        }
+
+        String protocolParameter = MimeUtility.getHeaderParameter(part.getContentType(), PROTOCOL_PARAMETER);
+
+        // for partially downloaded messages the protocol parameter isn't yet available, so we'll just assume it's ok
+        boolean dataUnavailable = protocolParameter == null && mimeMultipart.getBodyPart(0).getBody() == null;
+        boolean protocolMatches = isSameMimeType(protocolParameter, mimeMultipart.getBodyPart(1).getMimeType());
+        return dataUnavailable || protocolMatches;
+    }
+
+    public static boolean isPartMultipartEncrypted(Part part) {
+        if (!isSameMimeType(part.getMimeType(), MULTIPART_ENCRYPTED)) {
+            return false;
+        }
+        if (! (part.getBody() instanceof MimeMultipart)) {
+            return false;
+        }
+        MimeMultipart mimeMultipart = (MimeMultipart) part.getBody();
+        if (mimeMultipart.getCount() != 2) {
+            return false;
+        }
+
+        String protocolParameter = MimeUtility.getHeaderParameter(part.getContentType(), PROTOCOL_PARAMETER);
+
+        // for partially downloaded messages the protocol parameter isn't yet available, so we'll just assume it's ok
+        boolean dataUnavailable = protocolParameter == null && mimeMultipart.getBodyPart(1).getBody() == null;
+        boolean protocolMatches = isSameMimeType(protocolParameter, mimeMultipart.getBodyPart(0).getMimeType());
+        return dataUnavailable || protocolMatches;
+    }
+
+    public static boolean isMultipartEncryptedOpenPgpProtocol(Part part) {
+        if (!isSameMimeType(part.getMimeType(), MULTIPART_ENCRYPTED)) {
+            throw new IllegalArgumentException("Part is not multipart/encrypted!");
+        }
+
+        String protocolParameter = MimeUtility.getHeaderParameter(part.getContentType(), PROTOCOL_PARAMETER);
+        return APPLICATION_PGP_ENCRYPTED.equalsIgnoreCase(protocolParameter);
+    }
+
+    public static boolean isMultipartSignedOpenPgpProtocol(Part part) {
+        if (!isSameMimeType(part.getMimeType(), MULTIPART_SIGNED)) {
+            throw new IllegalArgumentException("Part is not multipart/signed!");
+        }
+
+        String protocolParameter = MimeUtility.getHeaderParameter(part.getContentType(), PROTOCOL_PARAMETER);
+        return APPLICATION_PGP_SIGNATURE.equalsIgnoreCase(protocolParameter);
+    }
+
+    @VisibleForTesting
+    static boolean isPartPgpInlineEncryptedOrSigned(Part part) {
+        if (!part.isMimeType(TEXT_PLAIN) && !part.isMimeType(APPLICATION_PGP)) {
+            return false;
+        }
+        String text = MessageExtractor.getTextFromPart(part, TEXT_LENGTH_FOR_INLINE_CHECK);
+        if (StringHelper.isNullOrEmpty(text)) {
+            return false;
+        }
+        text = text.trim();
+        return text.startsWith(PGP_INLINE_START_MARKER) || text.startsWith(PGP_INLINE_SIGNED_START_MARKER);
+    }
+
+    public static boolean isPartPgpInlineEncrypted(@Nullable Part part) {
+        if (part == null) {
+            return false;
+        }
+        if (!part.isMimeType(TEXT_PLAIN) && !part.isMimeType(APPLICATION_PGP)) {
+            return false;
+        }
+        String text = MessageExtractor.getTextFromPart(part, TEXT_LENGTH_FOR_INLINE_CHECK);
+        if (StringHelper.isNullOrEmpty(text)) {
+            return false;
+        }
+        text = text.trim();
+        return text.startsWith(PGP_INLINE_START_MARKER);
+    }
+
+}

app/core/src/main/java/com/fsck/k9/crypto/OpenPgpApiHelper.java

@@ -0,0 +1,28 @@
+package com.fsck.k9.crypto;
+
+
+import com.fsck.k9.Identity;
+import com.fsck.k9.helper.StringHelper;
+
+
+public class OpenPgpApiHelper {
+
+    /**
+     * Create an "account name" from the supplied identity for use with the OpenPgp API's
+     * <code>EXTRA_ACCOUNT_NAME</code>.
+     *
+     * @return A string with the following format:
+     *         <code>display name &lt;user@example.com&gt;</code>
+     */
+    public static String buildUserId(Identity identity) {
+        StringBuilder sb = new StringBuilder();
+
+        String name = identity.getName();
+        if (!StringHelper.isNullOrEmpty(name)) {
+            sb.append(name).append(" ");
+        }
+        sb.append("<").append(identity.getEmail()).append(">");
+
+        return sb.toString();
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/AlarmManagerCompat.kt

@@ -0,0 +1,19 @@
+package com.fsck.k9.helper
+
+import android.app.AlarmManager
+import android.app.PendingIntent
+import android.os.Build
+
+class AlarmManagerCompat(private val alarmManager: AlarmManager) {
+    fun scheduleAlarm(triggerAtMillis: Long, operation: PendingIntent) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtMillis, operation)
+        } else {
+            alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerAtMillis, operation)
+        }
+    }
+
+    fun cancelAlarm(operation: PendingIntent) {
+        alarmManager.cancel(operation)
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/AndroidKeyStoreDirectoryProvider.kt

@@ -0,0 +1,11 @@
+package com.fsck.k9.helper
+
+import android.content.Context
+import com.fsck.k9.mail.ssl.KeyStoreDirectoryProvider
+import java.io.File
+
+internal class AndroidKeyStoreDirectoryProvider(private val context: Context) : KeyStoreDirectoryProvider {
+    override fun getDirectory(): File {
+        return context.getDir("KeyStore", Context.MODE_PRIVATE)
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/ClipboardManager.kt

@@ -0,0 +1,22 @@
+package com.fsck.k9.helper
+
+import android.content.ClipData
+import android.content.Context
+
+/**
+ * Access the system clipboard
+ */
+class ClipboardManager(private val context: Context) {
+
+    /**
+     * Copy a text string to the system clipboard
+     *
+     * @param label User-visible label for the content.
+     * @param text The actual text to be copied to the clipboard.
+     */
+    fun setText(label: String, text: String) {
+        val clipboardManager = context.getSystemService(Context.CLIPBOARD_SERVICE) as android.content.ClipboardManager
+        val clip = ClipData.newPlainText(label, text)
+        clipboardManager.setPrimaryClip(clip)
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/CollectionExtensions.kt

@@ -0,0 +1,40 @@
+package com.fsck.k9.helper
+
+/**
+ * Returns a [Set] containing the results of applying the given [transform] function to each element in the original
+ * collection.
+ *
+ * If you know the size of the output or can make an educated guess, specify [expectedSize] as an optimization.
+ * The initial capacity of the `Set` will be derived from this value.
+ */
+inline fun <T, R> Iterable<T>.mapToSet(expectedSize: Int? = null, transform: (T) -> R): Set<R> {
+    return if (expectedSize != null) {
+        mapTo(LinkedHashSet(setCapacity(expectedSize)), transform)
+    } else {
+        mapTo(mutableSetOf(), transform)
+    }
+}
+
+/**
+ * Returns a [Set] containing the results of applying the given [transform] function to each element in the original
+ * collection.
+ *
+ * The size of the output is expected to be equal to the size of the input. If that's not the case, please use
+ * [mapToSet] instead.
+ */
+inline fun <T, R> Collection<T>.mapCollectionToSet(transform: (T) -> R): Set<R> {
+    return mapToSet(expectedSize = size, transform)
+}
+
+// A copy of Kotlin's internal mapCapacity() for the JVM
+fun setCapacity(expectedSize: Int): Int = when {
+    // We are not coercing the value to a valid one and not throwing an exception. It is up to the caller to
+    // properly handle negative values.
+    expectedSize < 0 -> expectedSize
+    expectedSize < 3 -> expectedSize + 1
+    expectedSize < INT_MAX_POWER_OF_TWO -> ((expectedSize / 0.75F) + 1.0F).toInt()
+    // any large value
+    else -> Int.MAX_VALUE
+}
+
+private const val INT_MAX_POWER_OF_TWO: Int = 1 shl (Int.SIZE_BITS - 2)

app/core/src/main/java/com/fsck/k9/helper/ContactNameProvider.kt

@@ -0,0 +1,16 @@
+package com.fsck.k9.helper
+
+import app.k9mail.core.android.common.contact.ContactRepository
+import app.k9mail.core.common.mail.EmailAddress
+
+interface ContactNameProvider {
+    fun getNameForAddress(address: String): String?
+}
+
+class RealContactNameProvider(
+    private val contactRepository: ContactRepository,
+) : ContactNameProvider {
+    override fun getNameForAddress(address: String): String? {
+        return contactRepository.getContactFor(EmailAddress(address))?.name
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/Contacts.kt

@@ -0,0 +1,16 @@
+package com.fsck.k9.helper
+
+import com.fsck.k9.mail.Address
+
+/**
+ * Helper class to access the contacts stored on the device.
+ */
+class Contacts {
+    /**
+     * Mark contacts with the provided email addresses as contacted.
+     */
+    fun markAsContacted(addresses: Array<Address?>?) {
+        // TODO: Keep track of this information in a local database. Then use this information when sorting contacts for
+        // auto-completion.
+    }
+}

app/core/src/main/java/com/fsck/k9/helper/CrLfConverter.kt

@@ -0,0 +1,9 @@
+@file:JvmName("CrLfConverter")
+
+package com.fsck.k9.helper
+
+fun String?.toLf() = this?.replace("\r\n", "\n")
+
+fun CharSequence?.toLf() = this?.toString()?.replace("\r\n", "\n")
+
+fun CharSequence?.toCrLf() = this?.toString()?.replace("\n", "\r\n")