K-9 Mail

Full-featured email client

New in version 18.0

K-9 Mail version 18.0

New:
- PNG avatars
- Setting to display ISO date/time in message list
- Fixed-width font for composing

Changed:
- Attachment summary moved to header

Fixed:
- "Delete (from notification)" setting did not retain state
- Find folder search hint text was cut off
- User not notified if offline when sending message
- CC/BCC fields were not expanded by default for Reply All
- Crash occurred when retrieving images
- Deleted messages could remain visible in message list

K-9 Mail is an open source email client that works with basically every email provider.

Features

* Supports multiple accounts
* Unified Inbox
* Privacy-friendly (no tracking whatsoever, only connects to your email provider)
* Automatic background synchronization or push notifications
* Local and server-side search
* OpenPGP email encryption (PGP/MIME)

Install the app OpenKeychain: Easy PGP to encrypt/decrypt your emails using OpenPGP.

Support

If you're having trouble with K-9 Mail, ask for help in our support forum.

Want to help?

K-9 Mail is a community developed project. If you're interested in helping to improve the app, please join us!
You can find our bug tracker, source code, and wiki at https://github.com/thunderbird/thunderbird-android.
We're always happy to welcome new developers, designers, documenters, translators, bug triagers and friends.

Donate

mzla.link/supportK9

Versions

Although APK downloads are available below to give you the choice, you should be aware that by installing that way you will not receive update notifications and it's a less secure way to download. We recommend that you install the F-Droid client and use that.

Download F-Droid

Version 18.0 (39035) suggested Added on Apr 16, 2026

arm64-v8a armeabi-v7a x86 x86_64

This version requires Android 6.0 or newer.

It is built and signed by F-Droid, and guaranteed to correspond to this source tarball.
Permissions
- view network connections
  
  Allows the app to view information about network connections such as which networks exist and are connected.
- take pictures and videos
  
  This app can take pictures and record videos using the camera while the app is in use.
- run foreground service
  
  Allows the app to make use of foreground services.
- run foreground service with the type "dataSync"
  
  Allows the app to make use of foreground services with the type "dataSync"
- run foreground service with the type "specialUse"
  
  Allows the app to make use of foreground services with the type "specialUse"
- have full network access
  
  Allows the app to create network sockets and use custom network protocols. The browser and other applications provide means to send data to the internet, so this permission is not required to send data to the internet.
- show notifications
  
  Allows the app to show notifications
- read your contacts
  
  Allows the app to read data about your contacts stored on your phone. Apps will also have access to the accounts on your phone that have created contacts. This may include accounts created by apps you have installed. This permission allows apps to save your contact data, and malicious apps may share contact data without your knowledge.
- read sync settings
  
  Allows the app to read the sync settings for an account. For example, this can determine whether the People app is synced with an account.
- run at startup
  
  Allows the app to have itself started as soon as the system has finished booting. This can make it take longer to start the phone and allow the app to slow down the overall phone by always running.
- Schedule precisely timed actions
  
  This app can schedule work to happen at a desired time in the future. This also means that the app can run when you're not actively using the device.
- use biometric hardware
  
  Allows the app to use biometric hardware for authentication
- use fingerprint hardware
  
  Allows the app to use fingerprint hardware for authentication
- control vibration
  
  Allows the app to control the vibrator.
- prevent phone from sleeping
  
  Allows the app to prevent the phone from going to sleep.
- com.fsck.k9.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION
Download APK 9 MiB PGP Signature | Build Log

New in version 17.0

K-9 Mail version 17.0

New:
- Account avatar customization
- Foldable device support
- Email messages can be printed
- Unified folder account indicator
- Display account avatar in message notifications

Fixed:
- Tap behavior was unreliable in recipient fields
- Device orientiation change duplicated recipient field text

Version 17.0 (39034) - Added on Mar 19, 2026

arm64-v8a armeabi-v7a x86 x86_64

This version requires Android 6.0 or newer.

It is built and signed by F-Droid, and guaranteed to correspond to this source tarball.
Permissions
- view network connections
  
  Allows the app to view information about network connections such as which networks exist and are connected.
- take pictures and videos
  
  This app can take pictures and record videos using the camera while the app is in use.
- run foreground service
  
  Allows the app to make use of foreground services.
- run foreground service with the type "dataSync"
  
  Allows the app to make use of foreground services with the type "dataSync"
- run foreground service with the type "specialUse"
  
  Allows the app to make use of foreground services with the type "specialUse"
- have full network access
  
  Allows the app to create network sockets and use custom network protocols. The browser and other applications provide means to send data to the internet, so this permission is not required to send data to the internet.
- show notifications
  
  Allows the app to show notifications
- read your contacts
  
  Allows the app to read data about your contacts stored on your phone. Apps will also have access to the accounts on your phone that have created contacts. This may include accounts created by apps you have installed. This permission allows apps to save your contact data, and malicious apps may share contact data without your knowledge.
- read sync settings
  
  Allows the app to read the sync settings for an account. For example, this can determine whether the People app is synced with an account.
- run at startup
  
  Allows the app to have itself started as soon as the system has finished booting. This can make it take longer to start the phone and allow the app to slow down the overall phone by always running.
- Schedule precisely timed actions
  
  This app can schedule work to happen at a desired time in the future. This also means that the app can run when you're not actively using the device.
- use biometric hardware
  
  Allows the app to use biometric hardware for authentication
- use fingerprint hardware
  
  Allows the app to use fingerprint hardware for authentication
- control vibration
  
  Allows the app to control the vibrator.
- prevent phone from sleeping
  
  Allows the app to prevent the phone from going to sleep.
- com.fsck.k9.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION
Download APK 13 MiB PGP Signature | Build Log

New in version 16.1

K-9 Mail version 16.1

Fixed:
- Messages containing complex CSS could be unreadable
- Deleted/read messages in unified inbox may not update until refresh

Version 16.1 (39033) - Added on Feb 10, 2026

arm64-v8a armeabi-v7a x86 x86_64

This version requires Android 5.0 or newer.

It is built and signed by F-Droid, and guaranteed to correspond to this source tarball.
Permissions
- view network connections
  
  Allows the app to view information about network connections such as which networks exist and are connected.
- take pictures and videos
  
  This app can take pictures and record videos using the camera while the app is in use.
- run foreground service
  
  Allows the app to make use of foreground services.
- run foreground service with the type "dataSync"
  
  Allows the app to make use of foreground services with the type "dataSync"
- run foreground service with the type "specialUse"
  
  Allows the app to make use of foreground services with the type "specialUse"
- have full network access
  
  Allows the app to create network sockets and use custom network protocols. The browser and other applications provide means to send data to the internet, so this permission is not required to send data to the internet.
- show notifications
  
  Allows the app to show notifications
- read your contacts
  
  Allows the app to read data about your contacts stored on your phone. Apps will also have access to the accounts on your phone that have created contacts. This may include accounts created by apps you have installed. This permission allows apps to save your contact data, and malicious apps may share contact data without your knowledge.
- read sync settings
  
  Allows the app to read the sync settings for an account. For example, this can determine whether the People app is synced with an account.
- run at startup
  
  Allows the app to have itself started as soon as the system has finished booting. This can make it take longer to start the phone and allow the app to slow down the overall phone by always running.
- Schedule precisely timed actions
  
  This app can schedule work to happen at a desired time in the future. This also means that the app can run when you're not actively using the device.
- use biometric hardware
  
  Allows the app to use biometric hardware for authentication
- use fingerprint hardware
  
  Allows the app to use fingerprint hardware for authentication
- control vibration
  
  Allows the app to control the vibrator.
- prevent phone from sleeping
  
  Allows the app to prevent the phone from going to sleep.
- com.fsck.k9.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION
Download APK 12 MiB PGP Signature | Build Log

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