Help finding who is hosting my email

Hello Everyone,

I am trying to: find our where this email is hosted, and delete this email account. We don't know where this email reside, where the server are. The owner told me that he opened this email in the 90ties when AT&T was called worldnet.  He has never used this email for the past 30 years but last week someone cracked his password and started sending him crazy emails. This email Kevinkeats@worldnet.att.net forwards the emails to his regular account. This is why we want to delete it because that email has no purpose anymore.

Who can help me to find where this email reside please : kevinkeats@worldnet.att.net. I called AT&T 2 times they don't find that email in their server. Neither network solution or godaddy. but that email is active somewhere.

I also need a webmail address so i can at least reset the password then delete that account.

thank you