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The Intelligent Message Filter

The built-in antispam features of Outlook and Exchange 2003 may be enough for some organizations, but many would say they are too basic for their Exchange environment. But before you rush out and invest money in an expensive third-party antispam solution, it’s a good idea to consider some details about Microsoft’s upcoming Exchange 2003 antispam add-on, which goes by the name Intelligent Message Filter (IMF) and should be released in the first half of 2004.

The IMF is based on the SmartScreen technology developed by Microsoft Research. The SmartScreen technology makes it possible for IMF to distinguish between legitimate e-mail and unsolicited e-mail or other junk e-mail. The SmartScreen technology’s first appearance was with Microsoft’s MSN Hotmail clients. SmartScreen tracks over 500,000 e-mail characteristics based on data from hundreds of thousands MSN Hotmail subscribers, who volunteered to classify millions of e-mail messages as legitimate or spam. Because of all the MSN Hotmail tracked e-mail characteristics, IMF can help determine whether each incoming e-mail message is likely to be spam.

Each incoming e-mail on an Exchange 2003 server with IMF installed is assigned a rating based on the probability that the message is unsolicited commercial e-mail or junk e-mail. The rating is then stored in a database together with the message and contains a message property called a spam confidence level. This rating persists with the message when it’s sent to other servers running Exchange and even other users’ inboxes.

It’s up to the Exchange admin to determine how IMF should handle e-mail messages. This is done by setting either a gateway threshold or a mailbox store threshold, both of which are based on the spam confidence level ratings. If the message has a higher rating than the gateway threshold allows, IMF will take the action specified at the Exchange gateway server level. If the message has a lower rating, it’s sent to the recipient’s Exchange mailbox store. If the message has a higher rating than the threshold of the mailbox store, it will be delivered to the user’s mailbox, where it then will be moved to the Junk E-mail folder.

Things Worth Noting About the IMF

Keep the following points in mind when you’re considering using the IMF:

  • The spam confidence level rating only can be used by Outlook 2003 and Exchange 2003 or later.

  • IMF can only be installed on a server running either Exchange 2003 Standard or Enterprise, not on Exchange 2000 and/or SMTP relay servers, as most third-party antispam solutions can.

  • IMF will only be available to software assurance (SA) customers.

  • IMF will be released in the first half of 2004.

  • IMF is heuristics-based and will therefore improve over time.

  • IMF will integrate with both Outlook 2003 and Outlook Web Access (OWA) 2003 trust and junk filter lists.

  • Spam confidence levels (SCLs) can be can be set by the Administrator.

For more information about Microsoft’s IMF, visit

Microsoft also has plans to extend and enhance the Exchange messaging environments with a release of a newly developed Simple Mail Transfer Protocol (SMTP) implementation that acts as a perimeter or edge guard. The Exchange Edge services will enable you to better protect your e-mail system from junk e-mail and viruses as well as improve the efficiency of handling and routing Internet e-mail traffic. If everything goes as planned, the Exchange Edge services should be released in 2005. For more information about Exchange Edge services, visit


As mentioned earlier, the IMF add-on will be available exclusively to customers enrolled in Software Assurance, so many organizations won’t be able to take advantage of it. Instead, they will have to invest in one of the third-party antispam products on the market.

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Inside the SPAM Cartel(c) Trade Secrets From the Dark Side
Inside the SPAM Cartel: By Spammer-X
ISBN: 1932266860
EAN: 2147483647
Year: 2004
Pages: 79

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