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Courier Mail Server vs Mailu: catalog facts
Courier Mail Server	Mailu
Free Free and open-source software.	Free Free and open source.
Linux, Self-hosted	Linux, Self-hosted
SMTP, IMAP, POP3, webmail and mailing lists in one package Components can be switched on or off individually	Webmail and admin interface included Per-domain delegation and quotas
Built from source on POSIX systems, with no Windows support Calendaring in the webmail is basic	Requires Docker Releases are infrequent
Self-hosted	Self-hosted
Open source	Open source
License not stated	License not stated
No account needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 24, 2026

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