I now need to figure out how to determine someone's IP address from their emails.
That's easy Bill. You want to "view headers" in your email program. If you have gmail, hotmail, or yahoo mail the option should be on the email when you are viewing it. Like "more options" "advanced" "view full headers", etc.
If you're using Outlook Express, right click on the message in your inbox > properties > details tab > message source button. You can copy the results to notepad. I used to do that before opening any suspect email in OE to see what the message actually contained, so I wouldn't infect myself with something.
I *think* that's how you do it in OE. I don't use it anymore, so my memory may be limited.