CC writes, “If I were to use XP Pro remote desktop to access my home computer and send an e-mail, would the home computer’s IP show as the e-mail sender or would it show the IP of the computer currently being used?”
As long as the email client you are using is on the remote machine, connecting to a PC via Remote Desktop (RDC) to send mail will result in mail that appears to come from the remote machine. In a scenario where you connect to your home machine over RDC while using your laptop from a coffee shop, the IP address your email is from will be the IP address of your home machine, because that’s the Internet connection being used to send the mail.
I was curious about this myself and while it intuitively made sense that the IP address should be the one for the remote machine, (not the one you are connecting from), I still had my doubts. I tested this scenario with my laptop at several coffee shops using both the public WiFi and my Cingular BroadbandConnect card. In all cases, the IP address the mail appeared to be from was the IP address of my cable connection at home.
This same scenario came in handy for me when I was in China recently and wanted to check something on Technorati (which is blocked in China). By logging into my home system with RDC, I was able to use Technorati over RDC because my home machine was outside the Chinese firewall.