Full-featured email client
About this app
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.
Licensed under Apache-2.0.
What's New in v20.1
Imported from the F-Droid repository index.
- K-9 Mail version 20.1
- Fixed:
- - Application could crash when rendering long messages
- - Application could crash due to memory exhaustion
Version history
Jul 7, 2026 · 10.1 MB · Android API 23–35 · code 39040
Imported from the F-Droid repository index.
- K-9 Mail version 20.1
- Fixed:
- - Application could crash when rendering long messages
- - Application could crash due to memory exhaustion
SHA-256 b57425d03ae8427b95a724214f35cec53d80e48aaeacd6e7f15cd5e92695fa10
Jun 24, 2026 · 10.1 MB · Android API 23–35 · code 39039
Imported from the F-Droid repository index.
- K-9 Mail version 20.0
- New:
- - Enable easily discoverable way to configure and use Thundermail
- Changed:
- - Only show message notification config actions above the cutoff
- Fixed:
SHA-256 fe507609b221796ddad80588159e65a688839974b9a7fa487f775fb5ba57a7c5
Jun 5, 2026 · 10.1 MB · Android API 23–35 · code 39038
Imported from the F-Droid repository index.
- K-9 Mail version 19.2
- Fixed:
- - K-9 Mail crashed when scanning Thundermail QR code
SHA-256 10a81c2a360868d1c26ab37c6225365b1ee02757ab8f90facb377560becfba55
Will it run on your device?
92%
- Runs on a broad range of modern Android versions.
- Multiple CPU architectures are covered.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be com.fsck.k9 is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 20.0 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall K-9 Mail first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of K-9 Mail, and a listing is removed when the evidence for it stops holding up.
Get K-9 Mail
Every source we list for com.fsck.k9 is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
b57425d03ae8427b95a724214f35cec53d80e48aaeacd6e7f15cd5e92695fa10
Signing certificate
c430665e3662253b2078dcda350c2c6ce44d915a3d8a147b63ced619bb9e8576
Permissions Required
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
Report a problem with this listing
A listing is only as good as its corrections. If a source is broken, a signature looks wrong, or this app should not be here, tell the moderation team.