MTA-STS Check
Validate secure SMTP transport policy.
What this test checks
_mta-sts TXT, HTTPS policy fetch, syntax, mode, MX patterns, max_age and TLS certificate.
Why this matters
The DNS signal alone is not sufficient: the HTTPS policy, certificate, mode, MX patterns and max_age all need to work.
How to fix common problems
Publish a valid policy that covers your real MX hosts before relying on enforce mode.
FAQ
Does MTA-STS guarantee encryption everywhere?
No. It applies to senders that support and successfully retrieve the policy.