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Pegasus Mail vs Claws Mail: catalog facts
Pegasus Mail	Claws Mail
Free Free to use; the developer accepts donations.	Free Free and open source under the GPL 3.0 or later.
Windows	Windows, macOS, Linux
Free with no paid tier Decades of continuous development	Opens and searches enormous mail folders without stalling Plugins for PGP, spam filtering, RSS and calendars ship with it
Windows only Traditional interface and slow release pace	Composes plain text by default; HTML mail sending is deliberately limited The interface is functional and looks like it was designed in 2004
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0-or-later
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 21, 2026

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