MTA-STS support Merged

Hello,

SMTP MTA Strict Transport Security (MTA-STS) is a mechanism enabling mail service providers (SPs) 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.

With this, for example, we can avoid MITM attacks by attackers that suppress STARTTLS commands / responses.

Microsoft & Google adopted this relatively young standard already.

Please look into supporting it too, with Domino.

More info:
https://datatracker.ietf.org/doc/html/rfc8461

Thanks!

Thibaud