Apps: K-9 Mail
Last updated: September 17, 2025
What K-9 Mail is a FOSS email client for IMAP/POP3/SMTP with built-in OpenPGP support. Package: com.fsck.k9.
Why on Zer0
- No proprietary services required; works with standard mail providers.
- Strong privacy defaults available (disable remote content, etc.).
Safe use
- Use IMAP over TLS and SMTP submission with STARTTLS or SMTPS.
- Disable remote images; enable plain text by default.
- Configure OpenPGP, use per-identity signatures, and verify keys.
- Keep attachment cache small; enable periodic cleanup.
Limits
- No native Exchange/ActiveSync; limited push on some providers.
- Some corporate mail setups may require additional steps or not work.
Links
- Website: https://k9mail.app
- F-Droid: https://f-droid.org/
- Store: Andromeda Store
Verify
- Install via F-Droid/Andromeda; confirm the repo signature.
- If sideloading, verify APK checksum and signing certificate.
- See: Verify