• Product: MailFrontier Anti-Spam Gateway 2.1.0.701
• Direct Price: $15 per user
• Company Info: MailFrontier Inc., 866-366-7726, www.mailfrontier.com

We were impressed with the customization capabilities in MailFrontier Anti-Spam Gateway 2.1.0.701 and even more impressed with its out-of-the-box performance. Without training or other administrative intervention, MailFrontier caught 93 percent of the spam we threw its way (the best in this roundup) while maintaining a respectable false-positive rate of just 0.5 percent.

Administrators will appreciate the LDAP schema-mapping tool that lets MailFrontier stay in sync with their network directory. The product supports Windows 2000 and 2003 Server, Solaris, and a large number of popular mail servers.

MailFrontier's administrator and user interface is Web based. Administrators have a great deal of control (although not quite as much as with Postini) over what the user experiences.

MailFrontier is the only product we tested to implement a user-voting system called collaborative filtering. One of the components in the calculation of whether a message is spam is the number of other users who have received that message and considered it to be spam.

There are numerous other factors in the spam calculation, including Bayesian filtering and heuristic analysis. If the threshold is crossed for a message, MailFrontier classifies it maybe junk or, if even higher, as junk. Either message type can be delivered, deleted, bounced back to the sender, marked as junk or maybe junk in the subject line, forwarded to another user, or stored in the Junk Box (a server-resident folder). At an administrator's option, the server periodically sends a message to each user listing the contents of his Junk Box with links to "unjunk" it.

Unlike some of the competition, MailFrontier does not include antivirus protection. But if you want to run filtering at your gateway, MailFrontier Anti-Spam Gateway is a good choice.