Hi Kara,
The best way to do something like this would be to use querystrings--for instance, if you're using Google Analytics, you would have your utm_medium values set for print/email. As such, you'd have URLs like
http://www.mydomain.com/belgium-event.html?utm_medium=email
As such, you can use querystrings to delineate traffic as well as form fillouts.
For your print piece, you can either use a redirect or a service like bit.ly to put something a little more human-friendly as the URL.