It seems Outlook now only supports OAuth login for office 365 and gmail accounts. Any other accounts can't make Outlook to popup an login form, even Yahoo mail. I've tried to make a 401 response including a HTTP header of "WWW-Authenticate: Bearer.... " to Outlook while the profile initialating, but it ignors the returned OAuth authentication URL and uses a fixed url(https://login.microsoftonline.com/common/oauth2/v2.0/authorize) which is dedicated for office 365 accounts.
I wonder if there is a way to make Outlook use a custom OAuth login URL which returned by the mail server.
