have you responded to their emails and has s/he/they acknowledged in any way that you did?

if they open the email you send to that accountl there is maybe something we could do to track'em down using a web-bug.

I’m not familiar with Yahoo mail but if its html based you can hide (embed) a one pixel transparent graphic in it that loads from a web server on yours or someone else’s computer. Keep that computer on and watch the logs for a request for that graphic. Being as the email is actually viewed on the computer that opens it.(the perp’s) you can get the actual ip of the computer its being viewed on and at least match that to an account. You might find their running kazaa and get a user name that way. There’s allot you can do once you find the ip/account.

If yahoo is text only you can title your email “do you want money?” and in the body set a link for a document /picture (set up same as above) and give some reason to entice them to click on it. Like maybe “ I think you should see this before you really get yourself in trouble” or “heres my financial situation”. Well you get the idea.