Sterna Mail

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.

It is private by default, pleasant to use, and fully free software (GPLv3). No tracking, no ads, no analytics, and no Google services required.

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 nine languages: English, French, German, Spanish, Italian, Portuguese, Dutch, Polish and Russian
* Screen-reader friendly, with settings export and import

Sterna Mail is open source, and its release builds are reproducible: F-Droid checks that the app it distributes is byte for byte the one built from the published source. The code can be read, audited, and improved by anyone.

Is Sterna Mail free to download?
Yes. The APK file linked from this page is free. The developer may offer in-app purchases once installed, but obtaining the installer itself costs nothing.

What Android version does Sterna Mail require?
Android 4.1+ or newer. Installing on older devices may cause crashes or refuse to install.

Is Sterna Mail safe to install?
We link to the exact APK published by emon. We do not modify the file. Still, as with any sideloaded app, scan it with a reputable antivirus before opening it, and only grant permissions the app genuinely needs.

How do I update Sterna Mail?
Install the newer version on top of the old one — Android will keep your data. If the signature differs, uninstall first (you may lose local progress).

Why is the app not installing?
Common causes: not enough storage, an older Android version than 4.1+, or a conflicting build already installed. Free up space, check your OS version, and uninstall any previous copy before retrying.

1. Tap the Download APK button above and save the file to your device.
2. Open your device Settings → Security (or Apps → Special access → Install unknown apps) and allow your file manager or browser to install unknown apps for this one file only.
3. Open the downloaded app.sterna.apk file from your Downloads folder.
4. Tap Install and wait for Android to finish.
5. Open «Sterna Mail» by emon and grant only the permissions it actually needs.
6. Revoke the "unknown sources" permission once you are done installing.

Note: this page hosts or links to the installer only. The application name, icon and description are provided for identification. All trademarks belong to their respective owners.