K-9 Mail
E-mail application for Android
From Wikipedia, the free encyclopedia
K-9 Mail is a continued[1] free and open source email client for Android. It is designed as an alternative to the stock email clients included with the platform; it supports both POP3 and IMAP protocols and supports IMAP IDLE for real-time notifications. The project is named after the Doctor Who character K9.[2]
| K-9 Mail | |
|---|---|
| |
| Original author | Jesse Vincent |
| Developers | MZLA Technologies Corporation, Christian Ketterer |
| Release | 27 October 2008 |
| Stable release | 20.0
/ 23 June 2026 |
| Written in | Java, Kotlin |
| Operating system | Android |
| Successor | Thunderbird for Android |
| Type | Email application |
| License | Apache License 2.0 |
| Website | k9mail |
| Repository | |
K-9 Mail has been renamed to Thunderbird for Android since October 2024.[3][4]
History
The source code was first published to its git repository on October 27, 2008[5] by Jesse Vincent and the first binaries were released to the public on the Google Code site the same month.[6]
In 2015 the project received $86,000 of funding from the Open Technology Fund.[7]
On 13 June 2022, it was announced that K-9 Mail had been taken over by MZLA Technologies Corporation, a subsidiary of the Mozilla Foundation with current maintainer Christian Ketterer joining the team, and plans for K-9 Mail to be rebranded as Thunderbird for Android following the completion of a feature roadmap, including sync with Thunderbird on PC, integrating Thunderbird's automated account setup system, message filtering, and improvements to folders.[8]
On 30 October 2024, the first stable release of Thunderbird for Android (Thunderbird Mobile) was launched as version 8.0.[4] Thunderbird for Android can be installed via Google Play and F-Droid, among others.[9] The Thunderbird team had planned in 2022 to maintain K-9 for one year after the release of Thunderbird Mobile, i.e. until roughly October 2025.[10]
On 6 May 2025, the stable version 10 of Thunderbird Mobile and the beta of version 11 were released.[11]
On 23 June 2026, the stable version 20 of Thunderbird Mobile and K-9 Mail were released.[12]
Reception
In the early 2010s it was widely reviewed, and was particularly praised in the media between 2011 and 2013 as a replacement for the default mail application.[13][14] At the time, it was a leading alternative Android app, often recommended[15] when a user did not want to use the default app. It was awarded the "Best App for Sending Email" in the 2010 "Best Android Apps" book.[16]
Features
- Works with IMAP, POP3
- Folder sync
- Encryption with OpenKeychain support
- Signatures
- SD card storage
