whitelist an e mail address

I am finding different information on comcast sites on how to whitelist an e mail address. Some say it can't be done and the best one can do is add to comcast's safelist. However, no other e mails will go through. On another comcast page, it gives instructions on how to add the spammed e mail address to an address book and the very last sentence states and then "add to whitelist"-with NO instructions on exactly how to whitelist. I'm totally frustrated. All I want to know is --is it possible to tell my comcast xfinity e mail to allow an e mail address into my inbox, not get spammed, but it also allows the rest of my e mails to go into my inbox.