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.
How to avoid or correct an OAuth failure caused by rejected cookies
First, verify your general setting for cookies in Thunderbird:
- Do > > > .
- Look at the checkbox .
Ifis 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 button to open the Exceptions - Cookies dialog.
- In the Address of website input box, enter https://accounts.google.com.
- Pick , then .
- Alternatively, accept all cookies:
- Set the checkmark for .
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.