More detail about the SMTP AUTH exception Microsoft has made:
SMTP AUTH Exception Smoothens Path to Removal of Basic Auth in Exchange Online
Last week’s announcement that Exchange Online will block basic authentication for multiple protocols on October 1, 2022, got some attention. Now the hard choices of what to do with clients and applications need to be made. To smoothen the path to remove basic authentication, Microsoft is making an exception for SMTP AUTH. Your scripts and multi-function devices will keep working after October 2022, but the writing is on the wall and eventually even SMTP AUTH will stop working.