Aster Mail: Encrypted Email

Aster Mail is a private, encrypted email app for astermail.org accounts.

Your messages are encrypted on your device before they leave it. The server stores ciphertext and nothing else, so nobody at Aster can read your mail, scan it, or sell what is in it. There are no ads, no trackers, and no analytics anywhere in the app.

Private by design
- End-to-end encryption between Aster users, using a post-quantum ratchet protocol
- Zero-access architecture: the server holds only encrypted content
- No ads, no tracking, no telemetry, no profiling
- Open source under AGPL-3.0, so anyone can audit what the app does

Email aliases
- Create an alias for each site you sign up for, and turn one off when it starts getting spam
- See which alias a message arrived on, right in the message list
- Import and export your aliases

Your own domain
- Send and receive on a custom domain, with DKIM signing handled for you
- Buy a domain from inside the app

Everyday mail
- Folders, labels, categories, and search across your whole mailbox
- Swipe actions and a toolbar you can customize
- Templates, signatures, scheduled send, and auto-forwarding
- Blocked senders, sender filters, and an allow list
- Encrypted offline storage, so your mail is there without a connection

Security
- Biometric lock
- Two-factor authentication and a recovery key
- Active session management, so you can sign out a device you no longer have

Notifications
- Private mode hides the sender and subject on your lock screen
- Quiet hours schedule when notifications arrive
- Per-folder muting

This F-Droid build contains no Firebase or Google Play Services dependencies. Push notifications are delivered through any UnifiedPush-compatible distributor, such as ntfy. Background polling takes over when no distributor is installed.

Aster Mail is free to use. Paid plans add storage, larger attachments, more aliases, and custom domains.

Source code: https://github.com/Aster-Privacy/Aster-Android