Bcc

I always wondered what the 'Bcc' field entry was for on an email message, and I found a website tonight explaining how and why to use it. If you add people's addresses to the 'Bcc' field as opposed to the 'To' field, the appearance of people's addresses will be exclusive to themselves. James Huggins, the guy who wrote the article explains it best:
http://www.jamesshuggins.com/h/web1/bcc_field.htm