You can protect the privacy of your e-mail messages and files by using a program called PGP (Pretty Good Privacy). Not that most have us have anything to hide, but as the program's author points out, if you have nothing to hide, why don't you send all your mail on postcards?
PGP is available (as of 1/30/2001) at http://web.mit.edu/network/pgp.html. The program is freeware, and runs under MacOS, Windoz, and several flavors of UNIX/Linux. If the MIT link doesn't work, try the PGP home site at http://www.pgp.com. The PGP freeware download should be there someplace.
The program lets you encrypt messages so that only the intended recipient can read them. It uses public key cryptography, in which two keys are used to encode and decode messages.
One of the keys is kept private, and is used for decoding messages. The other (the public key) is free for distribution, and is used to encrypt messages to the person who owns it. So you can only send secure messages to people whose public keys you have, and people can only send secure message to you if you have given them your public key.
If you want to try it out, install the software, import my public key into your keyring, and drop me a line.