Microsoft office365 is progressively removing Basic Authentication in favour of oauth2 approaches, which means users of aerc and office365 may need to use oauth2 to authenticate. However, no aerc configuration instructions are provided for oauth2 with Microsoft, and it appears the oauthbearer scheme implemented by aerc is not supported by Microsoft, in favour of xoauth2 which is not available in aerc.

Many configuration instructions exist that require app passwords or azure app registrations, but these are often disabled by administrators, and its unclear whether these work with aerc anyway.

If xoauth2 can be implemented for aerc that will enable authentication for many users of office365.