Unfortunately the only way to get your key back is by re-sending an e-mail with it to the original e-mail address. You can recover the password for your email by following the necessary steps.
If the e-mail is hosted by a major company like hotmail, live, yahoo, gmail or aol, you can use any online forms or contact addresses to recover your password.
If the e-mail is hosted by an ISP, you may need to call them and provide proof of ownership to recover your password.
Best of luck with it.