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Courier Mail Server vs Stalwart: catalog facts
Courier Mail Server	Stalwart
Free Free and open-source software.	Free Free and open source, self-hosted.
Linux, Self-hosted	Linux, Self-hosted
SMTP, IMAP, POP3, webmail and mailing lists in one package Components can be switched on or off individually	Modern JMAP support alongside traditional IMAP and SMTP protocols Rust implementation aims for security and performance
Built from source on POSIX systems, with no Windows support Calendaring in the webmail is basic	Requires self-hosting and server administration knowledge Newer project with a smaller ecosystem than long-established mail servers
Self-hosted	Self-hosted
Open source	Open source
License not stated	License not stated
No account needed	Not stated if an account is 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 22, 2026

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