What are you losing if your company isn't enrolled in SA? Since there are a number of excellent anti-spam products available for all versions of Exchange, you aren't missing much, other than a free anti-spam filter -- and free is a subjective term since you'd be paying for SA.

What is the IMF and why is it so special? And no, we're not talking about the Impossible Missions Force. The Intelligent Message Filter is based on Microsoft SmartScreen Technology developed by Microsoft Research. Developed in part as an answer to the overwhelming amount of spam received by Hotmail subscribers, SmartScreen technology distinguishes between legitimate email messages and unsolicited commercial email or other junk email by evaluating the contents of incoming mail for recognizable patterns.

It then assigns the message a rating based on the probability that the message is unsolicited commercial email or junk email. The rating is stored in a database along with the message and contains a message property called spam confidence level. This property persists with the message when the message is sent to other servers running Exchange and even other user's Inboxes. However, since only Outlook 2003 and Exchange 2003 support the spam confidence level rating, older Outlook clients won't benefit from this message property.

The Exchange administrator determines how the Intelligent Message Filter handles the messages by setting a gateway threshold based on the spam confidence level. When the message has a higher rating than the gateway allows, it handles the message. When the rating is lower, the message is delivered to the mailbox and is moved to the Junk E-mail folder by Outlook 2003 (also using SmartScreen technology), if it exceeds the mailbox threshold.

Microsoft calls it SmartScreen technology, but it's not unlike the Bayesian filtering technology found in many anti-spam filters. The Intelligent Message Filter supports the use of real-time black lists, global deny and accept lists, sender filtering, and inbound recipient filtering, all features found in third party filters.

The Intelligent Message Filter needs to be installed on Exchange 2003, while many third party solutions can be installed on Exchange 2000 or on an SMTP server at the edge of the network, removing spam (and viruses) from the email system before passing it on to the back-end Exchange server. If you don't qualify for the Intelligent Message Filter or use an older version of Exchange, there are many anti-spam programs on the market to choose from. For a list of excellent anti-spam applications, visit http://www.slipstick.com/addins/content_control.htm. For more information on the Intelligent Message Filter for Exchange 2003, see http://www.microsoft.com/exchange/techinfo/security/imfoverview.asp.

Diane Poremsky is the president of CDOLive LLC and a Microsoft Outlook MVP. She's author of Teach Yourself Outlook 2003 in 24 Hours (Sam's, 2003) and coauthor of OneNote 2003 for Windows (Visual QuickStart Guide). For questions or suggestions for future columns, write her at outlook@cdolive.com.