I've just upgraded to Thunderbird 38.0.1 from version 37.something, and I cannot seem to get OAuth2 to work with my existing GMail account. My settings were as follows: Username: my.account@gmail.com Server: imap.google.com Port: 993 Security: SSL/TLS Authentication: Normal password This worked and still works fine. However if I then change Autentication to OAuth2, save and restart Thunderbird, I get the following error message when trying to view my gmail folder: "The IMAP server my.account@gmail.com does not support the selected authentication method". I've tried googling but I can't seem to find any word on how to configure OAuth2 with GMail beyond switching it on. So any ideas on how to get this working?