Nir Sofer - 140KB (Freeware)
IPNetInfo is a small and lightweight utility, which allows you to easily find all available information about an IP address. This utility can be very useful for finding the origin of any unsolicited email that you may receive.
Simply copy the message headers from your email software and paste them into the IPNetInfo utility, IPNetInfo then automatically extracts all IP addresses from the message headers and displays the information about these IP addresses.
With IPNetInfo you can find information such as the owner of an IP address, the country/state name, IP addresses range, contact information, address, phone, fax and email information.
System requirements: Windows 98/ME/2000/XP/2003/Vista. *Note: You should allow outgoing connections on your firewall to port 43.