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Postmark Spam Check vs Mail Tester: catalog facts
Postmark Spam Check	Mail Tester
Free Provided free by Postmark.	Free Running a test from the website is free.
Web	Web
Quick SpamAssassin score without running SpamAssassin Usable in the browser or through a JSON API	No setup beyond sending one email to a given address Simple score out of 10 that is easy to read
Only gives a SpamAssassin score, not a full deliverability test Messages are sent to a third-party service for checking	Tests a single message rather than ongoing deliverability Little detail on the homepage about what each check covers
Web application, Hosted service	Web application
Closed source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Needs internet	Needs internet
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

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