The various suggestions on forums didn't help. I finally paid $38 for online help with an immediate answer (after about a 5 minute wait and a little confusion) .
Mailbox in the toolbar has an option of going offline for each server (?) I use. The Comcast server was offline. How it got there I am not sure. But I think that in a hurry the day that I lost incoming mail, a window popped up that I closed immediately without really looking at it, just assuming that if I didn't click on anything I wouldn't be changing anything. so it goes.
Need Email Help? Please post the following information in your post. Do you use XfinityConnect? The Full or Lite version? Do you use an email client? Which one? (Eg; Windows Live mail, Outlook, a smartphone etc.) Which browser/version do you use? And- have you cleared your browser cache? Which operating system? XP, Vista, Windows 7, Mac OS X Details of the problem you are having.