Thunderbird 91.8.0, released 5th April 2022, converts the authentication method of 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.
Do > > > > and ensure it is set to OAuth2.
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 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 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 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.
- Do > > > .
Check if the proper authentication tokens have been saved
> > > > .
- If account authentication was set to OAuth2 and the OAuth login was successful, you should see entries for each username (gmail account) of the form
- oauth://accounts.google.com (https://mail.google.com/ …)
- Note: The oauth entry is an OAuth2 authentication token, and not a password.
- If account authentication was set to OAuth2 and OAuth login was not successful, check your password entries for providers of the following form and delete them:
- imap://imap.gmail.com (imap://imap.gmail.com)
- smtp://smtp.gmail.com (smtp://smtp.gmail.com)
If you're still having problems, you can ask a question in Thunderbird support.