Glossary
What is MTA-STS
Definition
MTA-STS (SMTP MTA Strict Transport Security) is a standard that forces sending servers to deliver mail to your domain only over TLS and only to servers with a valid certificate, protecting against interception and tampering in transit.
The policy is served at “mta-sts.domain” over HTTPS and announced by a “_mta-sts.domain” TXT record. It is often paired with TLS-RPT for reports on TLS failures. It improves the privacy of mail transport.
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