Zip code

There is too parts to that question; why you have to do it at all and why you have to do it every time. For the first part it is because there are different severs for different locations. Webmail.east.cox.net may have the same email as webmail.west.cox.net but they are different websites. 

The second part has to do with what happens when you enter in y our zip. The site is supposed to save a cookie on your computer that remebers your zip for you so you don't have to put it in each time. If your browser is set to ignore cookies, or you have a antivirus that blocks it, then it never gets saved on your PC. What browser do you have? What kind of antivirus do you have?