Clarification: I had been using OAuth2 normally, with the previously stored token, for quite a long time. Part of the reason I went intentionally messing around was to try to trigger the OAuth2 authentication screens on purpose, so I could remind myself how that process looks. I hadn't needed to do this since originally configuring Thunderbird to access my Gmail account quite some time ago.
In list, located oauth:// token and removed it. Saved and closed and selected Gmail account to trigger an access. Actual results: OAuth2 window appeared with Google's authentication steps; Provided successful auth; shown notice of Thunderbird's access request and button to 'Allow' the access.
This guide is aimed at users employing Thunderbird or other non-Apple, non-Microsoft mail programs. IMAP, POP, Authenticated SMTP: These older email retrieval and sending protocols are used by a wide range of email programs on Windows PCs, macs, and mobile devices.While these protocols are capable of using modern authentication, in your case they are not currently configured to do so since. Thunderbird fails gmail OAuth2 despite correct credentialsHelpful? Please support me on Patreon: thanks & praise t. Jul 01, 2020 Thunderbird Now as an end user, start Thunderbird. Do not start configuring the account yet, as we first need to modify a Thunderbird setting to allow for successful Modern Authentication through a browser popup. Click the ‘hamburger’ menu to open the Options window. Scroll all the way down, and open the Config Editor. Because there is no dynamic registration for OAuth2 settings with Gmail, we (reluctantly) implemented this by adding the required GMail OAuth2 setup information directly in the Thunderbird code. For this to work, we had to have some method of determining what was, in fact, a GMail address that expected to use GMail OAuth2 settings.
Oauth Compatible Thunderbird
Since, I have had to change my authentication method for this account in Thunderbird to 'Normal password', and generate an 'App Password' to use with it from the management interface at accounts.google.com. I cannot make the OAuth2 method in Thunderbird work anymore.
Thunderbird Gmail Oauth2
In troubleshooting the fault, I later on took the step to remove Thunderbird's access to my account at accounts.google.com, which I now realize has the effect of invalidating all the other stored tokens for this purpose out in the wild. Thereby, I have managed to break OAuth2 access on all my Thunderbird instances across my PCs. I have had to revert to the described old 'App Passwords' based mechanism everywhere. This works, but Google deprecated the use of App Passwords as an account security concern. Google would prefer you to use OAuth2, if you can.