Addresses - XFinity

I, too, am unable to delete duplicate or no longer valid email addresses. I have read through all of the memos related to this problem and it appears Comcast does not have a solution outside of the periodic updates to my account. I have now had this problem for more than a year and these out-dated e-mails which I have attempted to delete are still appearing. These addresses do not appear in my address book, but only in my "To:" selection. As this seems to be a problem unique to Comcast, is it not possible on your end to correct this, even though the service is through another company? Do not feel after all this time Comcast had not gotten this problem resolved. Please advise.