Harness E-Mail
LearnTheNet.com
Articles and tutorials on how e-mail works, how to attach and open files, how to remove header information before forwarding an e-mail, e-mail netiquette, e-mail privacy, and more.
http://www.learnthenet.com/english/section/email.html

Everything E-Mail
E-mail tips, glossary, services, software, and more.
http://everythingemail.net/

How Computer Viruses Work
A detailed discussion of traditional and e-mail computer viruses, with tips on protecting yourself (and the people in your address book!) from their damaging effects.
http://www.howstuffworks.com/virus.htm

Fight Spam on the Internet
Anyone with an e-mail address is a target for unsolicited commercial e-mail, or "spam." This site details ways to avoid spam and various scams that may arrive in your e-mail inbox.
http://spam.abuse.net/

The International PGP Home Page
This site offers free downloads of the PGP (Pretty Good Privacy) software for use in encrypting e-mail.
http://www.pgpi.org/