K-9 Mail Icon

K-9 Mail 0.4

By Mozilla Thunderbird • January 07, 2026
Communication Universal Native (Java/Kotlin) 428.22 KB
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File Information

Package Namecom.fsck.k9
Version Name0.4
Version Code4
ArchitectureUniversal
Min Android VersionAndroid None (API None)
Main Activitycom.fsck.k9.activity.Welcome
FrameworkNative (Java/Kotlin)
File Size428.22 KB
Signature (SHA1)0F1F3252CBA1C94DDD6186DAD5A035E96C6EE5E3
File Hash (SHA256)170cdc337e9b85d3cb5f0473f6376eb432b9568a64bf8bf2b7a11fdcca97b155

What's New

- Sync logging limited to 24 hours
- Client certificate not displayed in SMTP settings
- "Enable debug logging" did not provide verbose logging
- Scrolling short email could trigger left/right swipe
- Landscape scrolling only worked in center of some screens
- IMAP folder operations broken with prefixes
- HTML/table rendering display broken
- Application crashed opening placeholder folder

App Description

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 at

forum.k9mail.app

Want to help?

K-9 Mail is now part of the Thunderbird family and remains 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

github.com/thunderbird/thunderbird-android

We're always happy to welcome new developers, designers, documenters, translators, bug triagers and friends.
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APK Permissions 7

  • android.permission.ACCESS_NETWORK_STATE
  • android.permission.INTERNET
  • android.permission.READ_CONTACTS
  • android.permission.READ_OWNER_DATA
  • android.permission.RECEIVE_BOOT_COMPLETED
  • android.permission.VIBRATE
  • com.fsck.k9.permission.READ_ATTACHMENT
APK Verified

The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way.

Developer

Name: Mozilla Thunderbird

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