I have been using Thunderbird for a few months and changed my Google Password(even though Im not quite sure if the error wasnt already occuring before that), but now when I go on Thunderbird it gives me a popup window that says "Enter credentials for name@gmail.com on imap.gmail.com". Theres a field for the email-adress, but when I click "Next" theres the following error: "400. That’s an error. The server cannot process the request because it is malformed. It should not be retried. That’s all we know." These are the things I tried: Entering the old or new Password. Checked if the config is set to OAuth2 in both incoming and outgoing servers and enabled on Gmail-Account. Deleted and tried to (unsuccessfully) reregister my Thunderbird-Account. The same error pops up when it checks my password after the configuration. I dont know if the password change is actually the cause, since I think I remember the error message appearing earlier today, before I changed the password, but Im not sure. Also, I have another account linked to my Thunderbird, with no changed credentials, and while there is no similar error message, thunderbird suddenly also has problems connecting to it and asks to retry a few times (3-4) before actually connecting everytime I open it.