The source code was first published to its git repository on October 27, 2008 by
Jesse Vincent and the first binaries were released to the public on the Google Code site the same month. In 2015 the project received $86,000 of funding from the
Open Technology Fund. 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. On 30 October 2024, the first stable release of Thunderbird for Android (Thunderbird Mobile) was launched as version 8.0. 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. On 6 May 2025, the stable version 10 of Thunderbird Mobile and the beta of version 11 were released. ==Reception==