The classic open-source email client for Android, now developed together with Thunderbird for Android.
Standard email client. Requests only mail-related permissions; blocks remote images by default and supports PGP encryption.
K-9 Mail is a full-featured email client for Android supporting IMAP, POP3, and Exchange (via WebDAV). It handles multiple accounts, unified inboxes, push mail via IMAP IDLE, and rich folder management. Message view is plain-text-first with optional HTML rendering and remote-image blocking — a meaningful privacy default. Encryption works out of the box with OpenKeychain (PGP), and settings can be exported between devices. Since joining the Thunderbird family, the app shares code and design with Thunderbird for Android while keeping the familiar K-9 workflows. It is open source (Apache-2.0) and contains no ads or trackers.
K-9 Mail by Thunderbird / K-9 Project — Communication app, 14 MB, requires Android 5.0+. Direct APK download on AppsDone, scanned for malware.