This video explains how to trace an email back to where it originated (or was sent from). This does not mean that the location the email came from is where the person who sent it is, but it does help to determine in most cases where an email was sent from. Information which you can use to determine the legitimacy of any email, spam or otherwise.
YOUTUBE VIDEO LINK
http://www.youtube.com/watch?v=LU649WNhFeE
Netclad Security 