We are 365 shop… I cannot think of one single time the 365 being down has affected us at all. Maybe you’re right I don’t know. Maybe your region is worse than my region.
Then I would gather you don't rely on mail like many of their customers. Just do a simple search of M365 outages and you'll get plenty just in the last year.
Maybe MS actually has support. The UI is so much worse than Google's (which is bad enough for communication compared to Slack) that you just cannot win though.
