Check what a domain publishes about email transport
MTA-STS lets a domain publish rules for encrypted mail delivery. SMTP TLS reporting gives sending services a way to report encryption problems. This tool looks up those records and, when present, reads the domain’s public MTA-STS policy over HTTPS.
The report describes published settings. It does not log into mailboxes, send messages, validate a complete DNSSEC chain or test the encryption of a particular delivery. Missing MTA-STS does not establish that email is unencrypted.