• Thunderbird for Android and K-9 Mail 17.0 and above: Android 6.0 (Lollipop, API 23)
• Thunderbird for Android and K-9 Mail 8.0 and above: Android 5.0 (Lollipop, API 21)
• K-9 Mail Version 5.7xx and above: Android 5.0 (Lollipop, API 21)
• 4.9xx-5.600: Android 4.0.3+ (Ice Cream Sandwich MR1, API 15)
• 4.802-4.8xx: Android 2.2+ (Froyo, API 8)
• 4.800-4.801: Android 4.4+ (KitKat, API 19)
• 4.503-4.7xx: Android 2.2+ (Froyo, API 8)
• 4.501-4.502: Android 2.1+ (Eclair, API 7)
• 4.393-4.4xx: Android 2.2+ (Froyo, API 8)
• 4.1xx-4.392: Android 2.1+ (Eclair, API 7)
• 3.990-4.0xx: Android 1+ (Base, API 3)
• 3.907-3.913: Android 2.1+ (Eclair, API 7)
• 3.906 and below: Android 1+ (Base, API 3)

Change Logs are available for each of the code branches under active development. These logs are updated with each release, and they may be viewed at the following links (Note: if you are using the NoScript Firefox add-on, you must "allow" these pages in order for them to display properly)

• 6.9xx Main (unstable) Development Branch.

• 6.8xx (current stable) Branch.

• 6.6xx Branch.

• 6.4xx Branch.

• 6.2xx Branch.

• 6.0xx Branch.

• 5.8xx Branch.

• 5.6xx Branch.

• 5.4xx Branch.

• 5.2xx Branch.

• 5.0xx Branch.

Release notes for earlier versions of K-9 Mail can be found below.

• 4.8xx Branch. [Note: The first two releases on this branch (4.800 & 4.801) will only install and run on Android 4.4 (KitKat). Later releases (4.802+) are compatible with Android 2.2+ (Froyo).]

• 4.590 Branch (This was intended to become the 4.6xx branch, but issues related to the release of Android 4.4 interrupted K-9 Mail's normal release process.)

• Some longtime users of K-9 have reported incredibly slow message display times in 4.4. We haven't yet gotten our hands on a device that exhibits the problem, so we haven't been able to develop a proper fix. One thing that has worked for everyone who's tried it is to long-press on the account name in the account list and select "Recreate Data" -- This will COMPLETELY ERASE the local copy of your mail and redownload a brand new copy of everything from your server. Any mail that's on your device but not on your server will be DELETED.
• Super-dense message lists are now only shown if you set the number of message preview lines to 0 in the global display settings and disable display of contact pictures.
• New Slovak translation
• Updates to Czech, Spanish, Finnish, French, Korean, Polish and Russian translations.
• Labels for SSL/TLS and STARTTLS have been clarified.
• Added autoconfiguration for Fastmail.FM
• Tightened up the account list display for narrow devices

• Restore K-9's super-dense message lists when contact pictures are disabled and the number of preview lines is set to 0.

• Fixed a typo that made the changelog not visible on version 4.406

• Add some Russian ISPs for autoconfiguration
• Performance improvements when opening messages and marking them as read
• Update the Play Store's URL
• Performance improvements to our message view
• Update the android-support library to the latest version
• Fix a bug where actions started from the message list context menu could act on the wrong message

• Updates to Catalan, Chinese and Russian translations
• Workarounds for some broken POP3 servers
• Performance improvements

• Fixed a bug that caused K-9 to crash on upgrade in certain limited circumstance
• Bugfixes for the new Folders menu item
• Fixes for several crashes reported on the Play store
• Tweaks to checkboxes and color chip display

• Fixed a bug that caused K-9 to crash on the Accounts page if you're using the dark theme. Sorry!

• Add additional shortcuts to the Folder list.
• Add an "empty trash" option to the Account context menu
• Fixes for several crashing bugs reported by Play Store users

• Never use extended notifications when privacy mode is enabled
• Remove submenu from the account context menu to work a bug in some Galaxy devices
• Fixes for several errors reported by Play Store users

• Switched to a more holo-themed user interface
• Added a split screen setting to display message list and message contents side by side
• Added dialog to show the changes since the last update of K-9 Mail
• Added screen to notify the user of database upgrades after updating K-9 Mail
• Improve integration with third-party apps

• Added rich notifications on Android 4.1+ devices
• Changed the notification icon (Android 2.3+ only)

• Removed "Manage back button" setting. The back button now always goes to the previously displayed screen.
• Added new color picker to select account colors
• Unified some account settings into "General Settings" and "Reading Mail"
• Removed "compact layout" setting

• Composing messages in right to left languages should now work better

• Add References and In-Reply-To header for forwarded messages

• Fixed inability to zoom out when viewing messages
• Added setting to automatically shrink messages to fit the screen width
• Improved display of messages decrypted with APG
• Removed "system zoom controls" setting (zoom controls will only be shown on devices that don't support pinch-to-zoom)
• Added work-around for the auto-scroll issue of the message view on Jelly Bean
• Moved "show all headers" into the menu of the message list
• Changed colors of the quote dividers

• Added message threading (note: this is not the same as Gmail's conversation view)
• Added a setting to display contact pictures in the message list
• Changed from chips to colored circles that also indicate the (un)read state
• Added pull-to-refresh to check for mail
• Use different background for read messages in message list

• Improved last folder update time formatting
• Added support for wrapping long folder names in the folder list

• Changed appearance of the unread widget
• Added support for "Unified Inbox" and "All messages" to unread widget

• IMAP: Added support for server-side search (currently limited to sender and subject)
• IMAP: Added support for $Forwarded flag

• Added notification on SSL certificate validation failures
• Worked around ">" getting included in URLs when linkifying text/plain emails
• IMAP: Fixed SPECIAL-USE detection of Spam folder
• IMAP: Fixed a bug that caused messages to be lost when "moved" to a non-existant folder

• Updated Japanese translation (Koji Arai)
• Updated Finnish translation (Jani Kinnunen)
• Updated Italian translation (Vincenzo Reale)
• Updated French translation (Erkan)
• Updated Greek translation (igavio)
• Updated Russian translation (Alexey)
• Updated Czech translation (Ondřej Vodáček, Jan Urbánek)
• Updated Hungarian translation (RootRulez)
• Updated Brazilian Portuguese translation (Marcio Zomb13)
• Updated Traditional Chinese translation (Leo Yang)
• Updated German translation (Danny Baumann)
• Updated Spanish translation (enriquefeas)
• Updated Dutch translation (Sander Bogaert)
• Updated Korean translation (Uni-)
• Updated Danish translation (l.meldgaard)
• Updated Catalan translation (Enric Morales)

• Automatic folder config for Yahoo!, Gmail, and other RFC6154 SPECIAL-USE-compliant servers
• Set the IMAP namespace for Gmail during auto-configuration
• Changed UI to allow selecting the empty IMAP namespace
• Set 'When I delete a message' to 'Delete from server' by default for IMAP on automatic setup like manual setup does
• Set default names for Archive and Spam on manual config like automatic setup does
• Added autoconfiguration settings for several providers

• Option to have confirmation on deleting starred messages
• Option to strip signature from quoted text in replies
• Extended setting to hide subject in notification area (never, when locked, always)
• Save settings changes "on pause" rather than "on back" so we actually save settings when a user hits home or menu or whatever
• Added font size setting for text input fields in the message composition screen
• Added a setting to disable marking messages as read on viewing
• Enable system zoom and disable gestures by default
• Add discard confirmation dialog when pressing back in message compose
• Option to now refuse to save drafts of messages marked as encrypted

• Added a button to switch the identity in the message composition screen
• Prompt user which email address to use when a contact with multiple email addresses was picked

• Fixed quoting of text/plain reply when sending text/html messages (builds plain reply separately instead of converting from the HTML)
• Forwarded messages always use the quoting style 'Header'
• You can now can have reply and signature before quote, reply and signature after quote, or reply before and signature after quote (setting reply after and signature before still corrects to both after)
• Convert quote characters in plain text messages to blockquotes in the HTML version. "Be like Thunderbird."
• Colorize quoted text that has been converted to HTML. Like Thunderbird, but optimized for mobile (no right margin quote bar, thinner left margin quote bar).
• Added 'From:' addresses on "reply all" even when 'Reply-To:' is set. Don't repeat address in 'To:' field if it's already included because it's the 'Reply-To:' address.

• Preserve header order (with the exception of duplicate headers like 'Received' they all show up where the first one did)
• Improved zooming/scrolling when viewing a message
• Added long-press popup menu to links in email message display
• Workaround to detect the charset from HTML mail without charset parameter on the header
• Added button to show unnamed and inline attachments

• Added batch buttons for 'Archive' and 'Move'. Made batch buttons configurable
• Remember the most recent sort setting in the message list
• Added a "sort by arrival" option

• Added widget to display the unread count for an account
• Added launcher shortcuts for special accounts/folders ("Unified Inbox" and "All messages")

• Fixed the parsing of response data for WebDAV requests
• Fall back to HELO command if the server doesn't know EHLO (SMTP)
• Improvements to mail sending timeout issues
• Yahoo! IMAP seems to no longer require 'ID ("GUID" "1")' over non-3G. See http://mobile.yahoo.com/mail for IMAP setup instructions.

• Support ACTION_SEND extras when handling ACTION_SENDTO. Too many applications get this wrong and rely on the undocumented behavior of the AOSP Email app and Gmail

• IMAP message UIDs are 32 bit unsigned values and cannot be stored in int, so we now parse them as long.
• Disable special screen reader mode on ICS. The default message view has special accessibility features already.
• Don't save to drafts if drafts folder is -NONE-
• Hide buttons & settings that don't do anything on POP3 accounts
• Delete attachment metadata and thumbnails when deleting attachments
• Reset unread/flagged count on "empty trash"

• Updated French translation (erkan2005)
• Updated Japanese translation
• Added Hebrew translation (elyashiv sabach - אלישיב סבח)
• Updated zh-rTW translation (Jeff117077)
• Updated Polish translation (Błażej Jeżewski)
• Added Greek translation (IGaviotis)
• Updated Turkish translation (wakeup)
• Added Danish translation (mittaa)
• Updated French and German translation (damor)
• Updated Russian translation (Dmitry Ashkadov)
• Added Ukrainian translation (Andriy Kopanytsia)
• Updated Spanish translation (AntonioGPS)
• Updated Chinese (zh-CN) translation (sunnavy)
• Updated Finnish translation (jkinnunen)
• Updated Italian translation (Votyer)
• Work around a bug in Android 4.x (?) when the system locale is Turkish

• K-9 4.009 fixes a catastrophic error that could cause mail stored on SD cards to vanish. We're really, really sorry we didn't catch this before 4.008 shipped.

• K-9 4.008 fixes a regression on Android 2.1 or earlier introduced in 4.007.

• K-9 4.007 includes a fix for a permissions issue on K-9's data files discovered (and fixed) by Ashley Willis.

• Upgraded the "read messages" and "delete messages" permissions from "normal" to "dangerous" to allow users and devices to better manage user data security.
• Fixed a rare NPE in autocompletion of email addresses.

• Fixed "mark as unread" from message view (Issue 3958)

• Fixed problem when importing multiple accounts
• Fixed bug that caused drafts to be lost under certain circumstances (Issue 3696)
• Fixed importing account settings for IMAP accounts (Issue 3986)

• Fix the swipe detection algorithm in message list. (Issue 3875)
• Fix crash when deleting an account. (Issue 3954)

• Show/hide ListView footer depending on message list type (Fixes issue 3946)
• Added new Danish translation

• Fixed a bug that stopped WebDAV support from working for many users

• Added ability to change the order of accounts (Issue 1251)
• Fixed counting of new unread messages

• Dynamically update the titlebar when the unread state of a listed folder changes (Issue 3177)
• Respect "move/copy destination folders" when selecting a target folder

• Search same sender from searchable folders instead of the unified inbox
• Switch subject to marquee ellipsis for landscape layout
• Properly keep selection in case of a configuration change (orientation, keyboard, etc.) during user interaction (e.g. a dialog)
• Reset visible limit when "clear messages" is used

• Improved support for picky/buggy apps when viewing attachments
• Rewrite broken MIME types to standard values (e.g. image/pjpeg to image/jpeg)

• Added support for requesting read receipts (Alessandro Russo)
• Added button to re-add the quoted text editbox after it has been removed
• Show (and populate) CC field when using "Reply all" on a message with recipients in the CC field (Issue 3509)
• Fixed restoring drafts saved with "Reply after quoted text" enabled (Issue 2568)

• Fixed bug with generation of HTML replies where no text was quoted
• Fixed bug where message was HTMLified when sent without quoted text but should have been sent as plain text (Issue 3530)

• Explicitly use Locale.US when dealing with dates in message headers
• Fixed parsing of messages with a very large header
• Make sure disposition size parameter is a valid number before using it (Issue 3712)
• Don't crash on messages without valid From-header (Issue 3683, Issue 3814)
• Fixed bug where invalid MIME boundaries could be created when using locales with difficult uppercasing rules (e.g. turkish) (Issue 3733)

• Added settings import/export
• Added account setting to configure whether or not to quote the original message by default
• Option to show next message after delete by default instead of previous
• Added 2MB, 5MB and "All" message download options
• Loosened the restrictions on the TLD to support custom private TLDs, as well as single label hostnames (Issue 2784) (rpimonitrbtch)

• Added Turkish translation (Recep PAYVERDI)
• Added Hungarian translation (Sándor Péter Nagy)
• Updated Catalan translation (dvbotet)
• Updated Dutch translation (Jan-Bart)
• Updated French and French Canadian translation
• Updated German translation
• Updated Japanese translation
• Updated Korean translation
• Updated Russian translation (Alexei Emanov)
• Updated Taiwan Traditional Chinese translation (Jeff117077)

• Disabled "download by date range" which caused messages outside the date range to be downloaded over and over
• Fixed bug where UID in response was truncated (Adam)
• Fixed some crashes

• Disabled "download by date range" which caused messages outside the date range to be downloaded over and over
• Don't open a connection to the POP3 server if a message is marked as read (since that's a local operation)
• Implemented work-around to handle malformed UIDL responses (Issue 3546)

• Treat 5xx SMTP return codes as permanent failures

• Don't crash when trying to connect to an non-SSL service using SSL (Issue 3798)

• Work around cases where mail was last checked in the future

• No longer suggest a display name based on the accounts configured in Android. Accordingly, no longer request the permissions android.permission.GET_ACCOUNTS and android.permission.READ_OWNER_DATA

• Stop service(s) if not in use (Issue 2777) (Christian Knecht)

• Added field UNREAD (João Pedro Taveira)
• Added field for sender address (Issue 3665) (Chris Banes)

• Fixed a bug that caused two Outbox folders to be displayed

• Fixed a bug that caused certain email messages to show up as "No Text"

• NPE fix in message list
• Restore support for Android 1.5

• Unavailable accounts are now greyed out

• You can now start typing to filter K-9's folder list

• Fixed display of colorized name in the message list.
• The date format preference is now refreshed each time the messages get listed. Previously, changes to the date format preference weren't noticed until the app restarted.
• Mark messages as ANSWERED only upon send.

• JPEG images with the MIME type "image/jpg" now open correctly on Motorola devices.
• Where a message has attachments, a long press on the "Save" button will allow the user to choose where to save the attachment to using either a file browser or by specifying a path; a short press saves to the default location (see "Configurability" below). Supported file browsers are OI File Manager, AndroidWorkz SystemExplorer, ES File Browser and Blackmoon File Browser (issue 1027).
• Fixes for downloading attachments

• Added an addressbook lookup button
• Explicitly set focus to "To:" input field when composing or forwarding a message.
• Made it possible to BCC to more than 1 address

• Fix display of icon in About box on Android 2.1 and earlier

• Use pre instead of div so that plain text clients get line wrapping correct.

• Correct encoding and decoding for the filename parameter in the Content-Disposition.
• Should store the disposition-type without Content-Disposition parameters.

• Implemented option to hide special accounts (issue 3060)
• Added option to disable confirmation dialog for "mark all as read" (issue 1415)
• Added "move to spam folder" confirmation dialog to MessageList
• Added "Save attachments to..." option to allow a default location for saving attachments (issue 1027)

• Updated Brazilian Portugese translation from noeczisto
• Added Catalan translation from David Valls
• Added a Galician (Galego) translation from fernando.coello@gmail.com
• Updated Chinese translation update from sunnavy
• Updated Finnish translation from Patrik Selin
• Updated Italian translation with patch provided by paolo.maccione
• Updated Japanese translation
• Added a Korean translation (from sungguk)
• Updated Polish translation from alekhavoc and rabbbit
• Updated Swedish translation from daniel.malmgren.DM
• Updated Spanish translation with changes provided by Hayawata
• Added support for emoji input in message subjects (on Japanese Devices only)
• Improved support for iso-2022-jp messages

• Remove trailing space from IMAP command as a potential fix to issue 3089.
• Fix length-check of BODYSTRUCTURE reply; fixes issue 3116.
• Unify two IMAP date parsing paths, improving the exception so we can learn what date format we don't cope with.
• Added another badDateTimeFormat to ImapResponseParser to handle IMAP servers that generate timestamps without a timezone. Fixed issue 3179.
• Fix bug with partitioning of IMAP FETCH commands

• In getPersonalNameSpaces now we ask the server for the real folder names corresponding to the special folders ids (for which we have constants), so we can map the account folders using the real names.
• Support non-English Exchange installations.
• Fix the ability to accept invalid SSL certificates for exchange support.

• Made the minor modifications to support CRAM-MD5 authentication in POP3 accounts.
• Disable "Enable refile buttons" preference for POP3 users

• New acounts now default to using the SMTP submission port (587) rather than the regular server-to-server (25) transport port.
• Permanent failures when trying to deliver a message move it back to drafts.
• Tempfail outgoing messages after 5 delivery attempts
• Opening a "permfail" message takes you to the drafts folder
• Split out "tempfail" and "permfail" message delivery errors
• Fix "sending message failed" notifications to actually report the server error
• If an SMTP server tells us how big the biggest message they accept is, don't even try to deliver a message to them if it's bigger than that size
• For a while, it was possible for users to configure their outbox and drafts folders to be the same folder. This could result in drafts being sent over and over. We now use the K-9 Identity header as a shibboleth for drafts, as it's not actually set when a message is sent.
• Removed some extra spaces from SMTP commands which picky servers rejected. Fixes issue 3182.
• Add options for PLAIN and LOGIN authentication even when not advertised by the server. Legacy PLAIN autoselection behavior is retained.

• AttachmentProvider can now return an attachment with an unmodified MIME type. However, when viewing attachments this is not desirable. So we try hard to return a sensible MIME type (use extension to look up a MIME type if it's originally "application/octet-stream"; or replace with canonical MIME type if it's known to be wrong, e.g. "image/jpg" -> "image/jpeg")

• Add extra for the sender address(es) to the "Share intent"
• Get rid of the "Fwd: " prefix when sharing a message. Add recipients to the intent ("To:" = EXTRA_EMAIL, "CC:" = EXTRA_CC)

• Change our technique for sending \r\n at the end of smtp commands to deal with a weird failure on honeycomb

• We have a test suite that can run (thanks to achen's start)

• Added an 'astyle' build target
• Switched the code's style back to something resembling AOSP standards
• switch build infrastructure to git
• Restore tools/build-beta to its former glory. It can now build a "K9 beta with different keys" that can sit next to an installed K-9.
• K-9 now compiles in the libs we only need at build time when building with eclipse. This is an annoying default, but it'll make life easier for newbies starting out with K-9 for eclipse. We should ALWAYS do release builds with ant

• Fixed polling schedule after SD cards are mounted or unmounted
• Fixed several NullPointerExceptions