Comment by proexploit

You could try contacting Yahoo about the email, I'm not sure how well that would work, but you've got tons to work with on the domain name.

You're you, he's not. Dispute the domain, how it's your name and your address: http://wdprs.internic.net/

Additionally check out http://www.icann.org/en/udrp/ if you want to go further.