dmarcexpert

Free tool

Free MTA-STS checker

Check a domain's MTA-STS policy and TLS-RPT reporting for inbound mail security.

What this checks

  • Whether the domain publishes an MTA-STS policy, and its mode (enforce, testing or none).
  • Whether the policy's MX patterns still cover the domain's real MX records.
  • Whether TLS-RPT reporting is set up, so you hear when something breaks.

MTA-STS protects the transport of mail into your domain, a different job from SPF, DKIM and DMARC. Learn the basics in MTA-STS and TLS-RPT explained. To see the full picture for a domain, run the DMARC checker.