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aerc vs Claws Mail: catalog facts
aerc	Claws Mail
Free Free and open source under the MIT licence.	Free Free and open source under the GPL 3.0 or later.
macOS, Linux, Command line	Windows, macOS, Linux
Composes in an embedded terminal, so you can read other mail while replying Built for the git mailing-list patch workflow, with diff highlighting and repo tabs	Opens and searches enormous mail folders without stalling Plugins for PGP, spam filtering, RSS and calendars ship with it
Terminal only, with vim-style keybindings to learn HTML mail rendering is a terminal browser, so complex newsletters look poor	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
Open source	Open source
License: MIT	License: GPL-3.0-or-later
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 21, 2026

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