[Users] Oauth2 not working with Microsoft Exchange

[David Fletcher]

A further thought on this issue - when you registered the app at the
Microsoft Azure portal, was there a choice about "Supported account
types"? See the instructions here:
https://learn.microsoft.com/en-us/graph/auth-register-app-v2

Did you set it as the Claws Mail FAQ says to "Accounts in any
organizational directory and personal Microsoft accounts"?

The more restrictive account type settings required a different
authorisation URL, of the format
https://login.microsoftonline.com/<tenant-name>.onmicrosoft.com/oauth2/v2.0/authorize

instead of the less restrictive one
https://login.microsoftonline.com/common/oauth2/v2.0/authorize.

If the client ID is linked to a more restrictive one Microsoft may be
kicking out the TLS request sent to the less restrictive one. I'd have
hoped it would give an error in that case, but maybe it doesn't and
just drops the connection?

David.