I am not sure if this is where this post should go but I was wondering if anyone knows of a program that tells you what ip address an email or a form is coming from. I am trying to start a site that allows only one sign-up per ip address. I also would love to know of a program that could display the machine id the machine id of a for the same reason. Thanks
You can determine a remote computers IP address for your site using PHP and Javascript.
As far as tracking e-mail origins, you'd have to check the headers. You don't actually recieve the e-mail directly from the computer that sent it.
Im sure there are programs that can extract them.
All in all it's probably easier to filter them by IP at the "sign up" page.
If you provide some more specific information about what you're trying to do, I could help you better.
tracking an ip address 
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