Ever wondered how many times an email is analyzed for all sorts of things? Today Exchange and Outlook on their own provide four layers just for SPAM filtering. Together these provide quite good protection but as we shall see using all of them might be unnecessary.

Exchange, Outlook and many third party products are all there ready to plug into the email flow. Is the email SPAM? Does it contain a virus, a Trojan, or maybe spyware? Any rude words in outgoing emails? The reasons for analyzing email content are only limited by our imagination.

Today I will just focus on anti-SPAM and will limit myself further to the protection provided by Microsoft. Even like that you will see just how the cocktail starts to get colorful. At the article introduction I promised you four protection layers just from Outlook and Exchange. The list that follows sorts the filters starting from the recipient client moving outwards towards the network edge. Clearly emails will meet these filters in the reverse order.

1. Outlook 2003 client side anti-SPAM filtering. SmartScreen technology provides the email content analyzing engine. This is combined with Safe Senders, Safe Recipients and Blocked Senders lists for a more effective filter.

   

   On installing Outlook 2003 filtering will by default be set to Low. Thus it acts only on emails with a high degree of certainty of being SPAM. Outlook 2003 relies on static filtering databases for which Microsoft provides periodic updates. This means that on installing Outlook 2003 today, the filtering technology will be fairly outdated unless you install the latest update (see references).

2. Exchange 2003 re-implements the per mailbox Safe Senders, Safe Recipients and Blocked Senders lists. For organizations with Outlook2003 this might not be immediately apparent. Why should the same functionality be implemented twice? This is necessary for organizations using earlier versions of Outlook or to handle the case when Outlook 2003 filtering is not available (more on this later).

   

3. Exchange 2003 Intelligent Message Filter (IMF). IMF is also based on SmartScreen Technology and again relies on periodic updates provided by Microsoft. When compared to other third party offerings IMF provides a stripped down server side anti-SPAM solution. Still, today with add-ons such as IMF Tune, IMFcompanion and IMF Archive Manager this gap has been bridged.

   

4. Exchange 2003 server level Connection, Sender and Recipient Filtering. This is the first line of defense to be applied right at the network edge.