> with a HSTS-like directive hosted in DNS. I think you are talking about MTA-STS (rfc8461) [0]. It is currently being adopted by the larger email services (Go

> with a HSTS-like directive hosted in DNS. I think you are talking about MTA-STS (rfc8461) [0]. It is currently being adopted by the larger email services (Google, Microsoft). MTA-STS is not 'hosted' in DNS, but published via a policy service over HTTPS, so it uses PKI. I work for Mailhardener, we offer MTA-STS policy services as a service [1]. We've seen an increased interest of MTA-STS recently, likely due to Microsoft announcing MTA-STS support [2]. [0] https://datatracker.ietf.org/doc/html/rfc8461 https://datatracker.ietf.org/doc/html/rfc8461 [1] https://www.mailhardener.com/blog/introducing-hosted-mta-sts https://www.mailhardener.com/blog/introducing-hosted-mta-sts [2] https://techcommunity.microsoft.com/t5/exchange-team-blog/introducing-mta-sts-for-exchange-online/ba-p/3106386 https://techcommunity.microsoft.com/t5/exchange-team-blog/in...