I created a (trial) azure account purely for the purposes of using oauth2 for signing into Microsoft 365 email accounts.
With this I have managed to get oauth2 to work (for IMAP and SMTP), for the email address of a user that I created in that azure account.
However it will not work for an email address created in someone else’s azure account for which I know the username and password.
When trying that address I’m also told that I have to add that email address as an external user.
When I do that it makes no difference, ouath2 still fails.

I set up Thunderbird and both addresses sign in using oauth2 with that without any issues.

So I think it’s my Azure set-up that’s the issue somehow
Is it because my azure account is a trial and not linked to a verified domain or something like that?
Also, is it necessary in general, to have a business azure subscription for oauth2 sign-in to Microsoft email addresses.
Apologies if I’m using terminology incorrectly, I’m new to oauth2