Over the course of the last decade or so, no single technology has had as much of an impact on the way people communicate as e-mail. Where once corresponding meant writing or typing out letters to be sent via the postal system, today electronic messages can be exchanged almost instantly - quite literally at the click of a button.
There's no denying that e-mail makes it amazingly simple to keep in touch with friends, family, and business contacts worldwide. However, this convenience comes at a price; e-mail is not a secure communication mechanism by default, and offers nothing in the way of true privacy or confidentiality. Every e-mail message that you send can potentially be intercepted, read, and modified by other users on its journey from the sender to the recipient. Compounding the issue, e-mail offers absolutely no guarantees that a message originated from the person listed as the sender. Others can send e-mail messages pretending to be you or anyone with whom you correspond.
Although the idea that someone else is reading or intercepting your e-mail is a little too "1984" for some people, the reality is that every single unsecured message you send or receive is at risk. Think of every normal e-mail message that you've ever sent or received. Then, ask yourself how comfortable you would feel if a third party was reading or collecting those messages, sending messages in your name, or pretending to be the person you're corresponding with. In the world of unsecured e-mail, each of these scenarios is not only possible, but also very easy to accomplish.
If you've ever used an e-mail client program like Microsoft Windows Mail, you've probably noticed a couple of buttons designed to encrypt and digitally sign messages. In this chapter you learn how secure e-mail systems work, how to configure your Windows Vista system to support secure e-mail, and ultimately how to make use of methods like encryption and digital signatures to secure the contents of e-mail messages and validate the identities of the people with whom you correspond.