if you mean about hiding email addies to keep hackers away, it was this.
when you forward, your entire message appears in the window. before you send it on, you can delete all the addresses that came before yours. so if you receive something with a string of addresses, you can delete them all, leaving only your immediate email address (at the top) and to whom it's going ( also at the top). BUT these are not included within the body of your email. hackers are getting into the body of the mail. i've asked my friends and family to do this before sending things to me, and they have. mac is petty safe in itself, but it can pass trouble on to others. if you still can't get your mind around it, pm me.