Sterna Mail

All your mail. None of the baggage.

Private email client for JMAP and IMAP/SMTP. No Google services, no tracking.

Free software under the GPLv3. No ads, no tracking, no Google services.

Named after the Arctic tern, which flies the longest migration of any animal. I liked the idea of mail that travels light and always finds its way home.

The protocol

Built for JMAP, fluent in IMAP

JMAP is the modern successor to IMAP. Instead of asking every folder what has changed, a single request brings back everything new, so mail arrives sooner and the battery lasts longer. Classic IMAP and SMTP work just as well, so no existing mailbox is ever out of reach.

IMAP IMAP: one round trip per folder, on every check

JMAP JMAP: one request, everything that changed

Guarantees

What it does, and what it doesn't

No Google, no FCM

New mail is pushed from your own server to your phone over JMAP EventSource, IMAP IDLE or UnifiedPush. Play Services are never required.

Nothing watches you

No analytics, no advertising, no crash reporting, no third-party SDK. The app only connects to hosts you chose or that a message you received names, and the project has no server of its own to receive anything.

Remote content blocked

Remote images and tracking pixels stay unloaded until you ask for them, and tracking parameters can be stripped from links before they open.

Reproducible builds

F-Droid rebuilds each release from the published source and checks it byte for byte against the app it hands you. Anyone can read and audit that source.

In daily use

A complete mail client

Sterna Mail is a private, modern email client for Android, built for JMAP, the faster successor to IMAP, with full support for classic IMAP/SMTP too. Adding an account starts from your email address alone: Sterna Mail works out the rest from what your domain publishes, and falls back to a manual form with the protocol and the server details when it publishes nothing. It fits JMAP servers like Stalwart as well as any standard mail provider.

Reading and organising

Unified inbox across multiple accounts (JMAP and/or IMAP/SMTP), fully offline with a local cache
Multiple JMAP accounts under a single login (delegated, shared or team mailboxes), each with its own folders, notifications and Sent copies
Conversation threading, nested folders, configurable swipe actions, stars, archive and delete with undo
Multi-select bulk actions, snooze, report spam, sort and unread-only filter
Search as you type, combining instant local results with server-side search, plus filters for sender, subject, attachments and date
Calendar invitations preview as an event card and go into your calendar app in one tap

Writing and sending

Compose with recipient autocomplete, multiple identities each with its own signature, attachments and drafts
Replies come from the address the message was sent to, with that identity's signature
Undo send, schedule send, and reminders for a forgotten attachment or a large recipient list
Opens mailto: links from any app or browser, prefilled

Accounts, notifications and encryption

Add an account with just your email and password (autodiscovery), password-free OAuth 2.0 sign-in, or manual IMAP/SMTP setup with provider presets
Push notifications for new mail with no Google and no FCM, over JMAP EventSource, IMAP IDLE or UnifiedPush, grouped per account and with quiet hours
OpenPGP encryption through an external OpenPGP app such as OpenKeychain, on both JMAP and IMAP/SMTP. Decrypted content is never written to disk, with attachments as the exception: one you open is written to the app's own storage until the cache is cleared, and one you save goes to the folder you pick and stays there. Printing a message, or saving it as a PDF, hands its decrypted text to the system print service
Remote images and tracking pixels blocked by default, and tracking parameters can be stripped from links before they open
Credentials encrypted with the Android KeyStore, app lock with biometrics or a PIN

Server features and polish

Server-side vacation responder, Sieve filter rules, and mailbox quota display
Material 3 interface with its own light and dark themes, optional Material You, and adjustable message text size
Available in ten languages: English, French, German, Spanish, Italian, Portuguese, Dutch, Polish, Russian and Simplified Chinese
Screen-reader friendly, with settings export and import

A look