Anyone who has launched an e-mail client to discover a glut of offers for dubious nostrums, bogus diplomas, and indelicate physical congress is well aware that spam - the junk mail that fills our inboxes in ever increasing amounts - is a huge problem.

The U.S. federal and state governments have made some efforts to curb the proliferation of spam, but these have been diluted by competing interests concerned with preserving and promoting free speech and allowing marketers to reach potential customers. Even the toughest antispam laws do little to stem the tide of spam--particularly spam that originates overseas, where American law holds no sway. ISPs have also stepped up efforts to snare the spam that slithers through their gateways, but these efforts are ineffective in most cases.

We looked at seven spam utilities:

1. Hendrickson Software Components' EmailCRX 1.6.2
2. Firetrust Limited's MailWasher Pro 1.1.3
3. Intego's Personal Antispam X4 (10.4.2)
4. Matterform Media's Spamfire 2.3
5. C-Command's SpamSieve 2.6.1
6. Bains Software's SpamSweep 1.5.3
7. JLS/JLSDevelopment's SpamX 3.0.2

We examined each utility's interface, ease of use, and mode of operation, and made some general judgments about its comparative effectiveness at eliminating spam--we say "general" because good spam filters get better with time and adapt to spam's changing nature. We then fed each program the same bucket of junk, to see how it dealt with some egregious forms of spam, right out of the box. In addition, we considered the following key questions:

1. Is the software easy to install and configure?
2. Which e-mail clients does it support?
3. Which e-mail systems does it support (POP, IMAP, or both)?
4. Does it deal with spam locally or remotely?
5. >Does it support a variety of spam-fighting techniques?
6. Is it easy to train (or is training unnecessary)?
7. Does it adapt to new forms of spam?
8. How configurable is it?
9. Are there hidden costs (such as paid subscription updates)?

Technology and techniques

These utilities interact with your e-mail client in different ways and use a variety of techniques for separating good messages from spam.

EmailCRX, MailWasher Pro, Spamfire, and SpamSweep download your incoming messages (or enough of each message to judge its content) and then filter and rate them. Once you've verified your mail, these utilities can delete the spam from the server and send the good messages to your e-mail client. EmailCRX and Spamfire act as proxy servers for your e-mail client; this means that when you ask your e-mail client to download your mail, it passes that task along to the spam catcher--which retrieves your good messages and passes them along--rather than going to your ISP's POP server.

While Personal Antispam X4 and SpamSieve are each full-fledged programs, they're integrated into your e-mail program. All your messages are delivered to your e-mail client; as they arrive, these utilities sort them into your inbox or into a spam folder, depending on their contents.

SpamX can allegedly either act as a proxy server or deal with your POP server as any e-mail client would. Regrettably, the proxy-server setup doesn't work with Apple Mail or the latest version of Microsoft Entourage.

Each of these utilities uses a variety of common techniques to filter spam. Nearly all include blacklists, whitelists, and a variety of statistical-learning filtering schemes. Some also have a "revenge" feature that lets you report spam to antispam agencies or to what the program believes is the spammer's ISP. (For definitions of some important spam-fighting terms, see How Do Spam Busters Work?.)

Designed for ease of use, SpamSweep--which installs an IP and domain-name blacklist, builds a whitelist of your approved senders, and offers Bayesian filtering--is the least configurable of the lot. The program provides no access to its blacklist, its spam corpus (the collection of words the Bayesian filter uses to identify spam), or its filters. Like other utilities that include Bayesian filters, it learns as it goes. Other than correcting it when it wrongly identifies messages as spam, you have no options for adjusting its behavior.   

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