Techie here...
There is no real way to call up something that tracks the IP addys of people that contact you. If you were a computer person, you could use some tools that come standard with Windows NT 4.0, or use a small program called a packet sniffer. What it does, is it analyses the incoming information packets to your computer and, in some cases, resolves the IP address in the Headers of the packet. Unfortunately, we are in the world of firewalls and routers, so the address you might get would be from that, instead of the address given to the internet is not the "true' address of the sender, but can get you closer by contacting a ISP with the IP you get.