One of the most common uses of encryption is in electronic messaging. Encryption can be used to secure email on public and private networks. Unlike e-mail on a private system, which goes directly to a mail server and resides there until it is retrieved, Internet e-mail bounces from server to server on its way to a recipient. This makes the transmission channel impossible to secure and provides numerous opportunities for interception. Here it makes sense to secure the message itself by using encryption. But private networks are not immune to the need for higher security and often employ encryption to guarantee the integrity of the message.
Sending plaintext email is like sending a postcard - what type of information do you disclose when mailing a postcard? When do you consider putting the letter in an envelope to resist tampering and to protect your privacy? Similarly, encrypting email is the first step to securing the contents of your message. One of the most popular methods of email encryption is the use of public key encryption.
The two most widely fielded methods of email encryption are PGP (Pretty Good Privacy) and Entrust. The former provides solutions for both individuals and corporations while Entrust focuses on the larger enterprise based secure messaging solutions. Also availabe to individual users/small businesses is encrypted email on a web based platform through Hushmail. This service allows you to send and receive email from their website, never having to buy any software or have the need for extra infrastructure.
Also available is S/MIME (Secure / Multipurpose Internet Mail Extensions) - a protocol that adds digital signatures and encryption to Internet MIME messages. The MIME format allows the body of the message to be text, graphics, audio/video, etc allowing one to encrypt multiple forms of newsgroup communications.
Encrypted mail enables the 'little guy' to decide how much privacy they want and when and where they want it. The Tools section has resources one could use for encrypted and anonymous email.