At this moment there are no MTA-STS support in postfix. But this thread [1] in postfix-users mailing list suggests acceptable solution: use external policy serv

At this moment there are no MTA-STS support in postfix. But this thread [1] in postfix-users mailing list suggests acceptable solution: use external policy server for MTA-STS discovery. I have implemented such server: package on PyPI [2], source on Github [3]. Works for me. [1] http://postfix.1071664.n5.nabble.com/MTA-STS-when-td95086.html http://postfix.1071664.n5.nabble.com/MTA-STS-when-td95086.ht... [2] https://pypi.org/project/postfix-mta-sts-resolver/ https://pypi.org/project/postfix-mta-sts-resolver/ [3] https://github.com/Snawoot/postfix-mta-sts-resolver https://github.com/Snawoot/postfix-mta-sts-resolver