I figure a bunch of people that get on this site are geek-proud. Therefore, I come to you with a problem. My company is getting hit by false emails coming from an ip address. They created a yahoo account with my company name as the username. Luckily, Yahoo passes the IP address of the sender (something that I did not know until today). I cannot find any information out on the ip address other than the ISP and general location. Does anyone know any other tools for figuring this out. I have tried:

DNSStuff.com and all of it's tools (ISP is roadrunner in the Spring, TX area)
I can telnet to it. It even accepts on port 25, therefore it may be a smtp gateway. Does not ack any HELO commands.
NSLOOKUPS 10 places on either side of the ip address.
Anyways, the IP is 67.78.107.162. If anyone can PM me any insight on who using this IP addy, I would appriciate it.