How do i find out somebodys ip address by using their email?

When you get a message from them, I assume you are using outlook or outlook express, just right click on the email. Go to properties, details, message source. The ip address should be there. But if it is not a static ip, it changes everytime they log on to the net.

"tom p" is absolutely right. An email address is not going to give you the IP address, even if you look at the email header. For the vast majority of internet users, their IP address is assigned temporarily when they connect to their internet service provider. When they disconnect, that IP address is assigned to the next person who connects. This is called dynamic addressing. Very few users (mostly huge corporate customers) have static IP addresses (meaning they never change). So, if you were to sign on to your internet connection 4 times in one day, you will likely have been assigned temporarily 4 different IP addresses.