I am in the process of switching email servers and wish to continue using the same email (custom domain). I have successfully set this up with the new server but cannot create a new Thunderbird account. I keep getting the same message: "Unable to log in at server. Probably wrong configuration, username or password." Everything is correct, however. I am wondering whether the issue is that there already is an account with the same email. It is no longer functional, but is it possible that Thunderbird will not accept the new account unless I delete the old one? I wouldn't do that, given that I keep my emails forever and often refer back to them. If this is my problem, how can I simply deactivate the old account? Or, if this isn't the problem, what is? Each time I click "re-test" on the Account Setup page, my server settings are confirmed. (I initially tried simply changing all the settings on the old account, without success.) ---- I think I've figured it out. The new server assigned a different password than the one I chose when setting up the account.