Having trouble with Yahoo Mail POP -- not able to receive email?

I'm very frustrated after two days of trying to figure out what's going on...beginning yesterday I could no longer receive email in my desktop mail client. Of course there no way to contact Yahoo, and they voluntarily give any indication that they're addressing the problem. At least Apple and Verizon were willing to work with me to determine it is a Yahoo Mail problem. Does anyone know what is going on and how to fix it????