MTA-STS Checker
Free MTA-STS Checker
Validates the MTA-STS TXT record and fetches the live policy file over HTTPS to confirm enforcement mode, max age and MX patterns.
MTA-STS Checker
TXT record, live policy file, mode and MX patterns.
Enter a domain above to run a real, live check.
Capabilities
What it checks
Live policy fetch
Actually retrieves https://mta-sts.<domain>/.well-known/mta-sts.txt, not just the TXT record.
Mode detection
Distinguishes none / testing / enforce — the real enforcement strength.
MX pattern list
Every host pattern the policy authorizes for inbound mail.
Why use it
Benefits
- Confirm mail delivery to your domain can't be downgraded to plaintext.
- Verify a policy rollout actually reached enforce mode.
- Export the check as JSON for a security review.
FAQ
Frequently Asked Questions
It forces sending servers to only deliver over verified, encrypted TLS to your real mail servers — without it, a network attacker can silently downgrade delivery to plaintext or redirect it.