from all my tests: because yahoo no longer requires a username at signup, us cox users didnt get a username for our accounts. because thunderbird requires a username in order to complete the config, we cant use the program for our cox email (we could before because cox requires a username for their site) i was using yahoo messenger basically since it started and still have access to my original account. i have just successfully setup thunderbird to use that email, because that account still has a username. overall: thunderbird needs to allow for email addresses in the username slot, so that us cox users can use it for our emails, otherwise we wont be able to.