Thunderbird was working for me wonderfully until about a month ago. I have several email accounts and had them all set up in Thunderbird. Then all of a sudden my ATT.net email no longer worked. Thunderbird no longer downloaded new messages for me. I had not made any changes to the account settings - it just stopped functioning. I've called ATT and verified that my username (the email address) and my password were correct. I can login to my ATT email using web mail, so I know the username/password combination is correct. Trying to correct the issue I deleted my old ATT account set up and lost all my old folders and emails, many of which I really needed. I have tried over and over to set up my ATT email in Thunderbird using the "Existing Mail Account" feature. It accepts my credentials, but when I click Done and the Checking Password message comes up, it tells me "Unable to log in at server. Probably wrong configuration, username or password." I use my ATT account as my business email. I seriously need to get it functioning correctly again. Can anyone help?