Questions to get to your answer:
Did your register another email address or has one been assinged to you?
Two, do have MS Outlook express since you may have POP server setup now requiring a email app to do so.
Best bet is contact them and see if these aspects apply.
Regular yahoo mail is free. So, since your paying with Yahoo as a affilate you may be getting more then you realize. Get the facts and if any apply let me know and I’ll be glad to guide you. Ciao!