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OpenSMTPD vs Haraka: catalog facts
OpenSMTPD	Haraka
Free Free and open source under the ISC license.	Free Free open-source software.
Linux, Self-hosted, Command line	Linux, Self-hosted, Command line
Part of the OpenBSD project Simpler than many other SMTP servers	High performance SMTP handling Flexible plugin system in JavaScript
A mail server, not a client for reading email Needs other components for a complete mail setup	Handles SMTP only; needs other software for mailbox access Customisation requires JavaScript knowledge
Downloadable app, Self-hosted	Downloadable app, 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 October 1, 2026

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