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Pegasus Mail vs Thunderbird: catalog facts
Pegasus Mail	Thunderbird
Free Free to use; the developer accepts donations.	Free Free forever, funded by donations.
Windows	Windows, macOS, Linux, Android
Free with no paid tier Decades of continuous development	Unified inbox across every account, or each account kept separate, your choice Mail, calendar, contacts and tasks in one application rather than four
Windows only Traditional interface and slow release pace	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
Closed source	Open source
License not stated	License: MPL-2.0
No account needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 20, 2026

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