Compare software

Postfix vs Exim: catalog facts
Postfix	Exim
Free Free and open source.	Free Free and open source under the GNU General Public Licence.
macOS, Linux, Self-hosted	Linux, Self-hosted, Command line
Security-focused design Runs on many Unix-like systems	Very flexible mail routing Extensive checks for incoming mail
Transfer agent only; needs a separate IMAP server for mailboxes Configuration requires mail server knowledge	Configuration is complex and differs from Sendmail A mail server, not a client for reading email
Self-hosted	Downloadable app, Self-hosted
Open source	Open source
License not stated	License: GPL
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 September 24, 2026	Official website Full listing and sources Checked September 24, 2026

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