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Claws Mail vs Pegasus Mail: catalog facts
Claws Mail	Pegasus Mail
Free Free and open source under the GPL 3.0 or later.	Free Free to use; the developer accepts donations.
Windows, macOS, Linux	Windows
Opens and searches enormous mail folders without stalling Plugins for PGP, spam filtering, RSS and calendars ship with it	Free with no paid tier Decades of continuous development
Composes plain text by default; HTML mail sending is deliberately limited The interface is functional and looks like it was designed in 2004	Windows only Traditional interface and slow release pace
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0-or-later	License not stated
No account needed	No account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 23, 2026

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