There are a few tools you can use:
http://www.dnsstuff.com/
The WHOIS, Reverse DNS, City from IP and IP Information should all be helpful. The tracert one may help as well.
There's also lots of good info on how to interpret email headers out there:
http://help.mindspring.com/docs/006/.../CIHDAIHF.php3
EDIT: Probably shouldn't post the IP here though, just for privacy reasons.