Edit: they (my Uni) made offlineimap unusable, but it works with davmail.
In my previous org I could also use offlineimap and msmtp to connect to their Microsoft mail server via standard protocols. But in this org I’ve so far tried the built-in Exchange support in Thunderbird as well as in Evolution Data Server based exchange clients (Evolution and KMail). All of them manage to connect to the server, kinda, but then I get an error message saying basically that my mail client is not approved and I’ll have to contact my admin to use it.
EDIT: I might add that the IT deliberately blocked non-Outlook mail clients a year ago or so, other Linux users told me that it worked fine before that. It’s supposedly a crackdown on people using shady third-party apps that they are concerned might exfiltrate data, but somehow they don’t allow exceptions even for reputable clients like Thunderbird.
Currently, only Thunderbird with the proprietary "OWL" extension somehow manages to connect despite the block. My understanding is that they somehow abuse the web interface to do so, instead of actually going through the proper protocols, but not sure.
If someone has another way to access Exchange servers that intentionally blocks non-Outlook clients I’d love to hear about it.