Microsoft 365 to start rejecting emails from on-premise unpatched Exchange servers.
Back in March 2023 Microsoft quietly mentioned that it would begin actively blocking inbound emails from on-premise exchange servers in order to maintain a certain level of security. Although more or us have moved to the cloud based solutions, if you still have an old(er) Exchange server running now may be the time to read up on the headaches about to hit you.
https://techcommunity.microsoft.com/t5/exchange-team-blog/throttling-and-blocking-email-from-persistently-vulnerable/ba-p/3815328
