After the browser, your e-mail client is the most-used attack avenue for organized computer crooks, script kiddie hackers, and slimy spyware distributors.

In fact, once upon a time e-mail was the way to get inside your system. Melissa, a 1999 virus that spread through the inbox, and the next year's I LOVE YOU Visual Basic-based malware, kicked off the days of massive attacks carried out via e-mail.

Although the days of such big-time attacks seem to be waning, the threat from malicious e-mail hasn't: It's simply shifted to phishing campaigns, spam that plants Trojan horses, and ploys to get users to visit Web sites where they can be infected.

We've set up five steps to locking e-mail against today's changed landscape, with suggestions specific for Outlook, and in some cases, for Thunderbird as well. The former, of course, is the Microsoft client packaged with the Office suite; the latter is an up-and-coming competitor from Mozilla, the outfit that also creates Firefox. The recommendations apply to other e-mailers as well, but you're on your own when it comes to specifics.

(For more security-centric "5 Ways . . . " check out earlier editions of the series, which include "5 Ways To Bulletproof Firefox," "5 Ways to Button Up Internet Explorer," and "5 Ways To Get Vista's Security Now.")

Step 1: Preview No More

Most of the time, attackers need help from users to wreak havoc. They have to convince them, say, to go to a Web site or to open an attachment. But some malignant messages are more insidious: they only need to be viewed to do damage.

Although your e-mail client's preview pane -- the part of the display that shows a portion of the message as soon as you point or cursor to the message in the inbox -- is a timesaver, you should close the pane. With preview turned off, you have to open the message to see it (and be infected by one of these attacks). It's not a foolproof defense, but at least it gives you the chance to read the subject line and see the sender without risk.

In Outlook 2003, select View|Reading pane|Off.

In Thunderbird, select View|Layout, and choose "Message Pane" so it's unchecked. (You can also toggle the preview pane off and on by pressing the F8 key.)