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OpenSMTPD vs Postfix: catalog facts
OpenSMTPD	Postfix
Free Free and open source under the ISC license.	Free Free and open source.
Linux, Self-hosted, Command line	macOS, Linux, Self-hosted
Part of the OpenBSD project Simpler than many other SMTP servers	Security-focused design Runs on many Unix-like systems
A mail server, not a client for reading email Needs other components for a complete mail setup	Transfer agent only; needs a separate IMAP server for mailboxes Configuration requires mail server knowledge
Downloadable app, Self-hosted	Self-hosted
Open source	Open source
License: ISC	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 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.