Microsoft has shared updated requirements for SMTP relay via its Exchange Online platform. The new updated requirement is not applicable yet and is set to roll out towards the end of the year.

Subject does most of the work here, but I'll expand. [edit] Maybe if I had just RTFM'd harder I would've found my answers... I think this will help, but leaving the post up in case anybody else has ...

Phishers taking advantage of Gmail’s SMTP relay service to impersonate brands Your email has been sent As the number of malware and ransomware attacks continue to become more prevalent, cybersecurity ...