Using classic Outlook for Windows in business environments
The mobile network vs wifi is a timing thing. Each time you connect, you get a random server at MS. Some are working fine, some are not. So if you toggle your wifi again, that time it might work fine on wifi, but not on mobile network.
They aren't blocking IPs so far as I can tell (except when you try too many times in a short period, it does seem to block it for a little while), it is just based on the server you get assigned by DNS randomly.