I am a long-time TB user with gmails. No problems in the past. I inadvertently hit send for my reply to a message delivered to me on a no-reply account (Wordpress). A big overlay screen popped up with the heading "sign in with Google" and then "sign in to continue to Thunderbird email"; then "enter email or phone"; and then "next". Clicking next takes you to a new screen that reads "Google 400, the server cannot process the request because it is malformed. It should not be retried. That's all we know." Meanwhile, TB tries to log on until it times out, ending with small box in lower corner of the screen, "Authentification error" (see third screen shot). I logged onto my Google account and as far as I can tell that is okay. I've turned off my computer and tried sending emails, but always get the above screens. Seems like I'm caught in a loop and can't cancel out the error message. Is this a TB problem or a Google problem. Help! Anyone answering this thread should email me at wetteraubruce1@gmail.com. I can read that email address on my laptop. Bruce Wetterau