Do you get those forwarded multiple times emails with a joke / cute picture / pithy saying all the way at the bottom? Does you email address appear in the cc not the bcc field, thus broadcast to the world?
Here is a simple free, no advertising nor graphics web page to get the message across about email netiquette.
Just reply with this link and you are done.
clipped from www.thanksno.com
Thanks. No.

Hi. The person who sent you this link is a friend who likes you a lot but who wants you to respect their email address, their privacy, and their time.

Chances are, this person asked you to visit this page because you did one of these things:
  • Forwarded a funny story, a virus warning, or a photo that you enjoyed
    		•
  • Sent email to lots of people using the “To:” line (instead of the “BCC:” line), thereby exposing your friend’s email address to strangers
    		•
  • CC’d your friend unnecessarily on something you had sent primarily to someone else
    		•
      blog it