Defines MTA-STS, a mechanism enabling mail service providers to declare their ability to receive TLS-secured connections and to specify whether sending MTAs should refuse to deliver to MX hosts that do not offer TLS with a trusted certificate. Published as _mta-sts.{domain} TXT record.
This RFC defines MTA-STS, a mechanism enabling mail service providers to declare their ability to receive TLS-secured SMTP connections.
SMTP MTA Strict Transport Security (MTA-STS) is a mechanism enabling mail service providers to declare their ability to receive Transport Layer Security (TLS) secure SMTP connections and to specify whether sending SMTP servers should refuse to deliver to MX hosts that do not offer TLS with a trusted server certificate.