Automatic Conversion of Google mail accounts to OAuth 2.0 Authentication

Thunderbird 91.8.0, released 5th April 2022, converts Gmail accounts to OAuth 2.0 to help users comply with Google's requirement of OAuth 2.0 for Gmail logins. These changes are required by Google.

If you have rejected cookies in Thunderbird, the OAuth process will fail because some cookies must be accepted for the OAuth 2.0 authentication flow to work properly. Without cookies to store data between page updates, the authentication flow cannot successfully complete the web pages served by Google. You need to accept cookies at least temporarily using one of the methods described below.

How to avoid or correct an OAuth failure caused by rejected cookies

First, verify your general setting for cookies in Thunderbird:

  • Do > Preferences > Privacy & Security > Web Content.
  • Look at the checkbox Accept cookies from sites.

If Accept cookies from sites is not checked, do one of the following and then go through the OAuth login process again:

  • Create an exception to accept cookies from Google:
    • Click the nearby Exceptions… button to open the Exceptions - Cookies dialog.
    • In the Address of website input box, enter
    • Pick Allow, then Save Changes.
  • Alternatively, accept all cookies:
    • Set the checkmark for Accept cookies from sites.

After you have gone through the OAuth process, if you prefer, you can again reject cookies, because receiving and sending mail will work with cookies rejected. But rejecting all cookies or removing the exception has the disadvantage that when the OAuth token for Gmail access expires at some date in the future, the OAuth dialog will show up and fail again until you accept the required cookies.

For greater detail about cookies, see the article Privacy panel - Remote content and cookie settings in Thunderbird.

If you're still having problems, you can ask a question in Thunderbird support.

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