Have you tried using the hardcoded Thunderbird (or similar) oauth credentials to authenticate to Google et al? You can also use davmail to proxy your requests to Office 365 / Exchange and it handles oauth also.
My organization also explicitly blocks access from other clients than Microsoft Outlook, even if the credentials are correct and the protocol is supported. They also refused providing an exception, citing that I can just use the web interface via Microsoft Edge on Linux. (Which I prefer not to do for many reasons, e.g. backing up my emails locally, working offline, and authoring using native tools.)
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.
I am surprised as davmail with the Exchange protocol has worked for me since I set it up. They made offlineimap unusable but davmail works (it even has a small web client for the login when more than a month has passed). ??
Edit: they (my Uni) made offlineimap unusable, but it works with davmail.
I actually haven’t tried DavMail (but have heard about it), so if it manages to get around this sort of shenanigans I’ll happily give that a shot.
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.
You are repeating the very same history and excuses (from the IT Dpt.) I lived and heard. Davmail works for me on Linux and MacOS even from outside the intranet. Give it a try and I would be happy to help, I have a gmail account with my nick.
