Rated 2 out of 5 stars

OK, but once you have connected to one google account - forget ever trying to change accounts. Even clearing the cache, uninstalling and reinstalling will not work. Totally unusable for me now as I set it up initially on the wrong google account. Shame.

This review is for a previous version of the add-on (0.5.1). 

Go to the add-on's options and check "Clear local data and authentication tokens", then restart Thunderbird. This will allow you to log in to a different account.