3.1 OAuth2 Users

If you've got 2FA authentication then there is a possibility of your provider supporting OAuth2 authentication.

If this is the case then you may require javascript.enabled to be set to true for the purpose of authenticating. After you've authenticated you may then disable it.

You will also require the mailnews.auto_config_url setting to be set to a value that contains the XML file for your provider. If you're concerned about contacting the Mozilla server, you could set this to some server that you control as long as the XML file for your provider is present.

Gmail now requires JavaScript for authentication. When you add a Gmail account to Thunderbird this option is presented when Thunderbird requests the auto configuration file.

OAuth2 authentication should be used and is preferred to using less secure methods of authentication such as application specific passwords.