First you will need to determine the provider in order to send it to their internal abuse inbox. If the spam came from someone@hotmail.com you would forward the email to abuse@hotmail.com. If you're using a web mail service (such as hotmail, yahoo, ail) you there should be a report as spam button come up on your top bar when you click on the email. Lastly, and perhaps most importantly, you
. should report it to the FTC. You can find more information here: http://www.ftc.gov/spam/