MTA-STS checker
Fetch and validate the MTA-STS policy.
The check runs on our server. We do not store the domain.
What this checks
MTA-STS (RFC 8461) lets a domain tell other mail servers "only deliver to me over TLS, and only to these servers." This tool reads the _mta-sts TXT record, then fetches the policy file it points to and reports its mode, allowed mail servers and cache lifetime.
What to look for
enforce means inbound mail must use TLS to one of the listed servers, or it gets rejected — no downgrade to plaintext or to a forged server. testing means the policy is being reported on but not yet enforced. none means a policy is published but has no real effect, which is a step people sometimes stop at by mistake, still exposed to the fallback to plaintext SMTP it's supposed to close.
No record at all
No _mta-sts TXT record just means MTA-STS isn't in use — most domains don't have one, and mail still works normally without it.