You can email customer support (Google it). But don't email them "Yo, My account name is XXXX wuts the email, bro?!" because 1) you look like a tool 2) You're going to have to provide a little information about the account than just the username because anyone can try to get an email from a username.
I would include; IP used to create, ISP used to create, Any stats etc, Recoveries if you made any, Date created.
I would not include; password.
Hopefully that helps.