Simple and maintainable Android e-mail client
About this app
Proof of concept e-mail (JMAP) client (pronounced \"Letters\"). Makes heavy use of Android Jetpack to be more maintainable than some of the other Android e-mail clients.
Features, and design considerations:
* Heavily cached, but not fully offline capable. Ltt.rs makes use of JMAP’s great caching capabilities. However, marking a thread as read does a round-trip to the server to update things such as read count. The action itself won’t get lost even if performed offline. * Account setup and done. Settings invite feature creep and its friend unmaintainability. There is one specific work flow. K-9 Mail or FairEmail is more suitable for others. * Minimal dependencies. Only widely known, highly tested libraries from reputable vendors. Third-party libraries are often of poor quality, and end up unmaintained. * First class Autocrypt. Ltt.rs fits right into its strict UX guidelines. * Based on jmap-mua, a headless e-mail client, or a library that handles everything an e-mail client would, aside from data storage and UI. There is also lttrs-cli, which uses the same library. * Looks to Gmail for inspiration in cases of uncertainty.
Licensed under Apache-2.0, by Daniel Gultsch.
What's New in v0.4.4
Imported from the F-Droid repository index.
- * Bundle Letsencrypt for older Android versions
Version history
Apr 13, 2025 · 7.3 MB · Android API 23–35 · code 19
Imported from the F-Droid repository index.
- * Bundle Letsencrypt for older Android versions
SHA-256 9c9060f3e26873147f6251b0c8325158c003199a1b0b710b5014b26937026e7b
Jan 11, 2024 · 7.3 MB · Android API 23–34 · code 18
Imported from the F-Droid repository index.
- * Enable predictive back gestures
SHA-256 6dfff21ddcc5d2b541728ef0df68d564350c7c0d06f42a709158a2186069810b
Dec 25, 2023 · 7.2 MB · Android API 23–34 · code 17
Imported from the F-Droid repository index.
- * Restore access to fastmail.com
- * Fix issue with notifications not showing
SHA-256 6fa471152ce71b145a2cd3d33d9e01d27ca0c227549bc36f99805b3489f8ce1d
Will it run on your device?
78%
- Runs on a broad range of modern Android versions.
- ABI coverage is focused on newer 64-bit devices.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be rs.ltt.android is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 0.4.3 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall Ltt.rs first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of Ltt.rs, and a listing is removed when the evidence for it stops holding up.
Get Ltt.rs
Every source we list for rs.ltt.android is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
9c9060f3e26873147f6251b0c8325158c003199a1b0b710b5014b26937026e7b
Signing certificate
9c2e57c85c279e5e1a427f6e87927fc1e2278f62d61d7fcefde9346e568ccf86
Permissions Required
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
Report a problem with this listing
A listing is only as good as its corrections. If a source is broken, a signature looks wrong, or this app should not be here, tell the moderation team.