So you want to use your professional @ulb.be email address in a non-Outlook application? Silly you, as if it would be straightforward and a well thought out entreprise-wide migration.
You see, I had a few (un)pleasant conversations about this with ULB's IT support.
IMAP and SMTP are disabled for being "unsafe" (ah yes, the age old standard is worse than Microsoft's proprietary bs but we'll get to that). As such, you cannot add your ULB email to any email app (desktop or mobile).
"But wait Dai! What about Microsoft's OAuth2 system? It surely works doesn't it?" Oh my sweet summer boy, of course it doesn't. As it turns out OAuth2 login attemps need to go through admin approval that gets rejected every time.