I had a Verizon tech set my ports etc however like others we keep getting Error 0X800CCC7D. I called Verizon Support and they doubled checked my settings, that they set up, and we still Error 0X800CCC7D after 5 or 6 emails.
I went to Microsoft's Forums and they pretty much say the same thing about Error 0X800CCC7D and that the only thing left that can be wrong is the ISP has some thing wrong, there are NO more options for the clients to do.
Verizon told us they are doing away with the Yahoo accounts and connections and now have their own email program that I have accessed. However before this we did not get Error 0X800CCC7D.