If you have forgot the email associated with your account you'll need to create a new account to solve the problem.
Once you create a new account, with an email address that you have access to, you must create a ticket. To create the ticket follow the below steps:
Go to http://xat.com/ticket and click Open New Ticket
In help topic select Lost Access
In subject, you have to write a message of 5 words or more that explains the problem. (e.g: I lost access to my account)
In message you are going to describe your problem with the primary account.
Click Open Ticket.
You will now receive an email when there are responses to the ticket. Volunteers will ask you some account security questions, you need answer it and I am sure they will be able to help you.