Email not working

I was a customer of Comcast and I stopped my service last year. But I was told that I will be able to use my email address as long as I log in consistently. I use my Comcast email multiple times a day. Since April 2nd I have all of a sudden stopped receiving and emails and went I try to sent myself an email it says mail box doesn’t exist. I called xfinity and spoke with multiple people but no one has helped. Any suggestions? Thank you