Sterna Mail

byPsychopath · Communication

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8.0

android

AI summary

Privacy-focused email client for JMAP and IMAP/SMTP with no ads or tracking. Supports multiple accounts, unified inbox, OpenPGP encryption, push notifications without Google services, and full offline use. Version 1.5.8 adds per-account notification channels, faster thread actions, JMAP sub-address support, and app-icon compose shortcut.

Generated by AI. May contain inaccuracies.

About this app

A fast, private JMAP email client for Android, fluent in classic IMAP/SMTP too. No ads, no tracking, no Google.

A complete, daily-drivable email client: read, organise, search, write, schedule, and send mail (with attachments) over JMAP or IMAP/SMTP, across multiple accounts, fully offline-capable, with OpenPGP encryption, push notifications, and remote content blocked by default.

Features

Reading and organising

- Unified inbox across multiple accounts (JMAP and/or IMAP/SMTP), fully offline with a local cache - Conversation view with collapsed threads and message counts - Nested folders shown as a collapsible tree; create, rename, and delete subfolders - Configurable swipe actions, star, archive and delete with undo, multi-select bulk actions, snooze, report spam, empty trash (with undo) - Sort and unread-only filter - Search-as-you-type with server-side and instant local results, plus advanced filters (from, recipient, subject, has-attachment, date) - Calendar invite preview as an event card with one-tap addition

Writing and sending

- Compose with recipient chips, autocomplete, email validation, multiple identities, attachments, and drafts - Undo send, schedule send, and reminders for missing attachments or large recipient lists - Opens mailto: links from any app, prefilled with addresses, subject, body, cc, and bcc

Accounts and setup

- Add an account with email and password using JMAP autodiscovery - Password-free OAuth 2.0 sign-in (device flow or authorization code with PKCE) - Manual IMAP/SMTP setup with provider presets and a test connection option - Per-account colour, sync window, and sync switch - Encrypted credential storage with AndroidKeyStore and app lock via biometric or PIN

Encryption

- OpenPGP via an external app such as OpenKeychain - Read and send signed and/or encrypted mail (PGP/MIME) on both JMAP and IMAP/SMTP - Decrypted content is never written to disk, with opened attachments stored in app cache until cleared

Notifications and server features

- Push for new mail with no Google or FCM: JMAP EventSource, IMAP IDLE, or UnifiedPush - Grouped per account, with quiet hours - Two home-screen widgets for unread count and recent mail - Server-side vacation responder and Sieve filter rules - Mailbox quota display

Appearance

- Sterna's own Arctic (light) and Pelagic (dark) palette, with optional Material You - Adjustable message text size, settings export and import - Screen-reader-friendly interface

Languages

Dutch, English, French, German, Italian, Polish, Portuguese, Russian, Simplified Chinese, Spanish

Respects the system language out of the box, and can be overridden per-app in Settings → Appearance.

Privacy

No tracking, no ads, no analytics, no Google services. Remote images and tracking pixels are blocked by default. Tapped links can be stripped of tracking parameters and confirmed before opening.

Requirements

- Android 8.0 (API 26) or newer - A JMAP or IMAP/SMTP mail account

Disclaimer

Sterna Mail is an independent, open-source project. Its interface is freely inspired by K-9 Mail (now Thunderbird for Android). It is not affiliated with K-9, Thunderbird, or any third-party service. All trademarks belong to their respective owners.

License

GNU General Public License v3.0

email open source privacy offline encryption jmap

What's new

v1.5.8Sep 19, 2026

Notifications
Each account now has its own new-mail notification channel, so you can set its sound and importance separately in Android settings. Send failures get their own channel. - Note: If you had silenced the old shared "New mail" channel or changed its sound, the new channels start from the default sound. Check each account once after updating.
Message list
Archiving, deleting, moving, marking as spam, or swiping a collapsed thread now removes rows immediately instead of waiting for the server. Refused rows come back. - With two or more accounts, tap the account name in the list's title to switch accounts. A small arrow shows it's tappable.
Composer
Long-press the app icon for a "New message" shortcut. - On JMAP servers with an address book, recipient suggestions now include its addresses, after recent ones and before phone contacts. - Fixed an issue where signatures with an address in angle brackets could lose it; retype it if it was saved in an earlier version. - Fixed an extra blank line in imported HTML signatures; re-import if needed.
Sending
On JMAP, plus-tagged sub-addresses (name+tag@example.com) are now sent under your identity with the From you typed. - Retry is no longer offered on a message that is already being sent, preventing double delivery.
IMAP
Only a top-level INBOX is treated as the inbox, not nested folders. - Fixed move retries on servers without MOVE that could leave duplicate copies. - On servers without UIDPLUS, a cut-off delete is completed on the next delete in that folder.
Account setup
Automatic JMAP setup now tries mail., jmap., and api. subdomains when the bare domain is unreachable.
Reading
When a sender's unsubscribe link opens a web page, the button now reads "Unsubscribe (web page)".