Recovering my Grandad’s email address?

I created an email address for my Grandad a while ago, however he doesn't check them very often. He has recently applied for some tickets and he should be receiving an email however, when I try to sign into his account it says that the email address is not valid. All I need is to be able to find out what happened to the email address, and if I created a new account with the same email would he receive all of the emails he previously received? I tried to talk to live support but they didn't seem interested at all and immediately sent me here. Is there anyone that can help with any suggestions. Any help would be greatly appreciated.