Comment by junaru

> firewall azure ranges

This will happen naturally as users change their credentials on server but not on outlook. Outlook proxy will try wrong password for 5 or so times and will get their IPs banned. This will affect many more users using the same server.

This will generate tickets for you and you will direct them to use plain local IMAP clients instead.

This whole idea at Microsoft was clearly forged by someone who has never served mail and is bound to fail as it trips standard security practices present for decades.