Compare software

Gridlink MailK-9 Mail
Free

Free and open source under GPL-3.0.

 Free

Free and open source.

Android Android
  • Supports JMAP and classic IMAP and SMTP
  • Includes JMAP contacts and calendar support with CardDAV and CalDAV alternatives
  • Open source with a long track record on Android
  • Now the foundation for Thunderbird's official mobile app
  • Android only
  • A fork of Sterna Mail with a separate release and support path
  • Android only, no iOS version
  • Interface is more utilitarian than modern polished mail apps
Downloadable app Downloadable app
Open source Open source
License: GPL-3.0 License: Apache-2.0
No account needed Not stated if an account is needed
Not stated if it works offline Not stated if it works offline

Checked October 8, 2026

Checked September 22, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.