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Haraka vs OpenSMTPD: catalog facts
Haraka	OpenSMTPD
Free Free open-source software.	Free Free and open source under the ISC license.
Linux, Self-hosted, Command line	Linux, Self-hosted, Command line
High performance SMTP handling Flexible plugin system in JavaScript	Part of the OpenBSD project Simpler than many other SMTP servers
Handles SMTP only; needs other software for mailbox access Customisation requires JavaScript knowledge	A mail server, not a client for reading email Needs other components for a complete mail setup
Downloadable app, Self-hosted	Downloadable app, Self-hosted
Open source	Open source
License not stated	License: ISC
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 1, 2026	Official website Full listing and sources Checked September 24, 2026

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