• Product: MailFrontier Matador
• Direct Price: $29.95 direct
• Company Info: MailFrontier Inc., www.mailfrontier.com

If you follow the war on spam, chances are you've heard about MailFrontier Matador and its challenge messages. You can configure the app to send mail automatically to unknown senders, asking them to identify the number of kittens in a digital photograph. If they reply correctly—automated mailing programs theoretically can't—they're whitelisted.

Challenge messages are only a small part of Matador, however, and if you're worried about annoying friends or colleagues—or losing legitimate business mail you've opted to receive—you can turn them off. Matador blocks spam via message analysis as well.

Much like Cloudmark's SpamNet, Matador adjusts its filters using data collected from its user community. The app adds two buttons to each user's e-mail client, so they can identify what they consider spam. But if you'd rather not depend too heavily on the opinions of others, you don't have to: You can scale back the collaborative filter and carefully customize your own set of message filters. Six controls help you govern what gets through.

In the past, when we've tested Matador's message-filtering abilities, it has always had a slight problem with false positives. This time out, the problem worsened. It mistakenly blocked 14 percent of legitimate messages. Moreover, the program didn't catch as much spam as it should have. Twenty percent of junk mail messages slipped through its filter. But that doesn't mean Matador isn't worthy of consideration. We like its powerful, easy-to-use interface. With more training, Matador's performance is likely to improve.