If you want to send a reply to a fraud email and trace where it goes there are several methods you can use, none of which are foolproof and many are quite ,"Noisy".
You could request a read receipt from the recipient. Few email readers automatically send a receipt but many promt the user to send one in response to a request. If youyr fraudster is a little dim they may not read the prompt and just click OK.
You could insert a web bug into a HTML email. You can use a <img> tag for a 1x1 transparent gif, with an image URL to your web server for example and look at the access logs to see which IP address requested the image. Depending on the recipient mail client you may also be able to execute JavaScript although most web based mail readers filter out client side scripting.
Several companies offer email tracking services which combine several techniques to give you an IP address, a read confirmation and details of how long the recipient spend reading the email. Check out
www.ReadNotify.com who offer a free trial of their service so you can check it out.
Regards,
Jim