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Mailpit vs Postmark Spam Check: catalog facts
Mailpit	Postmark Spam Check
Free Free to download and run.	Free Provided free by Postmark.
Web, Self-hosted, Command line	Web
Single binary or Docker image with no dependencies HTML compatibility, link and spam checks built in	Quick SpamAssassin score without running SpamAssassin Usable in the browser or through a JSON API
For testing only, not a real mail client Spam scoring relies on a SpamAssassin setup	Only gives a SpamAssassin score, not a full deliverability test Messages are sent to a third-party service for checking
Downloadable app, Self-hosted	Web application, Hosted service
Open source	Closed source
License not stated	License not stated
No account needed	Not stated if an account is needed
Works offline	Needs internet
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked September 23, 2026

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