I tried both. The error from davmail suggests it was specifically blocked/prohibit and I failed using actual Thunderbird.

Hi, I guess you have already tried.

My Uni also made it difficult but I succeeded in setting up a working davmail, using the exchange protocol.

Mail my username at gmail.com if you think I can help.

Gateway: Exchange Protocol: O365Interactive OWA or EWS (Exchange) URL: https://outlook.office365.com/EWS/Exchange.asmx

(follow the instructions at https://davmail.sourceforge.net/faq.html)