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Ltt.rs vs Thunderbird: catalog facts
Ltt.rs	Thunderbird
Free Free and open source under the Apache 2.0 licence.	Free Free forever, funded by donations.
Android	Windows, macOS, Linux, Android
Native JMAP support Simple, focused interface	Unified inbox across every account, or each account kept separate, your choice Mail, calendar, contacts and tasks in one application rather than four
Works only with JMAP servers, not IMAP Described as a proof of concept	The interface carries a lot of history and can feel dense next to a webmail tab Major ESR releases have historically been disruptive for add-ons and settings
Downloadable app	Downloadable app
Open source	Open source
License: Apache-2.0	License: MPL-2.0
Not stated if an account is needed	No account needed
Needs internet	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 20, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.