Open source Thunderbird email is coming to Android

Millions of Thunderbird desktop users can soon expect to see an official Thunderbird app for Android.
Written by Liam Tung, Contributing Writer
Image: Getty/MoMo Productions

Thunderbird, the open-source email application, is coming to Android thanks to the K-9 Mail Android email app project, which is joining Thunderbird to become the Thunderbird Android email app. 

Two years ago, Mozilla Foundation moved Thunderbird to its subsidiary MZLA Technologies Corporation in a similar ownership structure to Firefox under the foundation's subsidiary, Mozilla Corporation. The new subsidiary allowed the Thunderbird project to plot its own path with new features like OpenPGP end-to-end encryption and a long-awaited mobile app. 

According to the Thunderbird team, talks between Thunderbird product manager Ryan Lee Sipes and K-9's lead maintainer Christian Ketterer over a possible collaboration for a Thunderbird email app started in 2018. 

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Fast forward to 2022, the two have decided the best path forward is for K-9 to simply join Thunderbird rather than Thunderbird building its own app from scratch. 

"Many Thunderbird users have asked for a Thunderbird experience on mobile, which we intend to provide by helping make K-9 amazing (and turning it into Thunderbird on Android). K-9 will supplement the Thunderbird experience and enhance where and how users are able to have a great email experience. Our commitment to desktop Thunderbird is unchanged, most of our team is committed to making that a best-in-class email client and it will remain that way," Thunderbird said.

This means K-9 will take on the Thunderbird name and branding. But first, K-9 Mail will need to be aligned with Thunderbird's feature set and visual appearance.      

"To accomplish that, we'll devote finances and development time to continually improving K-9 Mail. We'll be adding brand new features and introducing quality-of-life enhancements," the Thunderbird team said in a blogpost.

K-9 isn't a hugely popular email app on Google Play but has had five million downloads from the Google Play Store. 

The roadmap for K-9 Mail currently includes: creating account setup using Thunderbird account auto-configuration; improved folder management; support for message filters; and syncing between desktop and mobile Thunderbird.

While Thunderbird acknowledges there's been demand for a Thunderbird app on iOS, the project only says in an FAQ that it is currently "evaluating" that option. 

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The team says it remains committed to desktop Thunderbird and that K-9 Mail will be "brought in-line with Thunderbird from a feature perspective, and we will ensure that syncing between Thunderbird and K-9/Thunderbird on Android is seamless."

The Thunderbird team also plans to offer Firefox Sync as as an option to sync accounts between Thunderbird and K-9 Mail. This should be implemented in summer 2023. 

The project is also exploring what Thunderbird features to bring to the Android app, such as support for calendars, tasks, feeds and chat.

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