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Free-GPGMail vs Gpg4win: catalog facts
Free-GPGMail	Gpg4win
Free Free and open source under the GPL-3.0 license.	Free Free software, funded by donations and public contracts.
macOS	Windows
OpenPGP encryption and signing inside Apple Mail No support plan purchase needed	Kleopatra gives GnuPG a real key manager instead of a command line Integrates with Outlook through GpgOL and with Explorer through GpgEX
macOS and Apple Mail only Unofficial build that may lag behind GPGTools releases	Windows only OpenPGP key management is genuinely hard, and the concepts do not hide well behind a GUI
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: GPL-2.0
No account needed	No account needed
Works offline	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.