I followed this advice from the Thunderbird website and it worked for me:
One detail often overlooked is the User name: some providers require the full email address, some the part before the @, and some accept either one. I never allow the setup wizard to enter the account settings, as they are often incorrect or obsolete. Select File/Offline/Work Offline to go offline, then File/New/Existing Mail Account, enter your credentials, Continue, then Advanced config. to enter the settings manually. Once the account is set up, remember to uncheck Work Offline.