The forum answer that was posted did not work for how to delete/remove and old email. It said; go to users, then list of accounts, then edit, then suspend. The tab users did not list all email addresses, only one
You need to use the Primary UserID to administer other IDs. Check your UserIDs on your home system with the lookup tool at https://idm.xfinity.com/myaccount/lookup. After you enter the requested information you'll see a list of the UserIDs on your account and an indication of which one is Primary.
If the ID you are using is not Primary, you'll need to log in with the Primary ID. If you need help with that, or if your ID is Primary but you still don't have access, contact one of their reps at the phone number on your bill or 1-800-Comcast, or chat with them at https://support.xfinity.com/chat and have them fix the problem.