You should be able to look at the email headers and either track back to the IP of his home connection, or the IP of the email service provider he uses. From th

You should be able to look at the email headers and either track back to the IP of his home connection, or the IP of the email service provider he uses. From there you give the info to the police and get them to issue a warrant or two to get the physical address of where it was sent. If you're lucky they wont have used a proxy to hide their real IP, and wont have used a public access point. Think about any apps you might have running which connect to services online automatically. I have an app which synchronizes my bookmarks with an online service (xmarks.com). I'd be tempted to contact them and ask for an IP address history of my own account to see if I could collect any other IPs that they might have used.