Same problem here. 2 chat sessions (Where the response was "Not our problem contact Microsoft or Contact Thunderbird." (I've been using Outlook 2003 and decided to change Thunderbird because I figured that might solve the problem)
Then a phone call to support and after discussing and trying 2 different port settings she logged a help ticket as she noticed a growing number of people reporting the same issue.
So as of 11:00PM Central - Still no success. I've tried a variety of different settings but no good. The best I get is "Connected to Cox smtp" but it keeps processing until it times out.