Microsoft is committed to providing world-class email security solutions and the support for the latest Internet standards in order to provide advanced email protection for our customers. Today we ar...
Updated Oct 16, 2023
Version 2.0
Blog Post
just to confirm what Viktor_Dukhovni mentioned, for anyone on O365 it's possible already to setup MTA-STS (as long as they keep the certificates valid).
Personally I did setup the mx as:
mx: *.mail.protection.outlook.com
The reason behind this is that Microsoft asks for a MX publication with <domain>-<tld>.mail.protection.outlook.com from their "wizard".
The only issue at this moment is that this works when the G-Suite platform (internet, MTA-STS capable) is communicating with (to) the O365 platform, not the other way around (O365 > G-Suite).
To properly contribute to the email ecosystem internet standards need to be implemented from a sending AND receiving perspective, so both parties (Google & Microsoft and others) need to play ball.