As you may know, I use Thunderbid as may main desktop email program. I use it with various email providers, including Gmail.
Everything worked fine up until this morning. I received mails to the Gmail account and was able to browse mails and compose them as well.
About an hour ago I started to get a popup informing me that I had to sign in to the Google account again.
The dialog did display the URL the request came from, it was a Google URL, so I knew it was legitimate. Also, checking to see if I could still access Gmail content in Thunderbird, I noticed that I could not.
I entered the Gmail email address and password, and was redirected to a "cookies disabled" page instead of the second verification step of two-factor authentication.
I tried again and same result. That was quite puzzling as I did not make any changes to Thunderbird.
When I checked the cookies setting in the email client, I noticed that cookies were disabled. That was the reason for me not being able to sign in and authorize the Gmail account for use in Thunderbird.
Note: While I experienced this with Gmail, you may experience it with other email services that rely on cookies for authentication.
Here is how I fixed the issue:
- Open the Thunderbird email client.
- Select Tools > Options > Privacy.
- Check whether "Accept cookies from sites" is enabled, or if the mail server is listed as an exception.
The accept cookies from sites preference was disabled in Thunderbird. I did not do it, and I'm not sure how it reset itself on its own.
Anyway, I enabled the option again, and made sure that third-party cookies are not allowed. I entered the Google account information again and it worked this time. Got the second authorization step and regained full access to the Gmail account in Thunderbird.
The same method works for any other email account, and also for calendar syncing. If you have added Google Calendar to Thunderbird for instance, you may run into the same issue. You may also use the same fix to correct the issue.