The details can be found here (thanks to the M&M queens!)
I’ve skinnied their instruction down just for quick reading::
1. Download & Install IMF – go to http://www.microsoft.com/downloads/details.aspx?FamilyId=C1B08F7B-8CAF-4147-B074-8C9C8F277071&displaylang=en
In ESM, go to Global Settings, right click Message Delivery, Properties, tab Intelligent Message Filtering, and configure your various thresholds. Example: set gateway treshold to 5, blocking messages to Archive and SCL rating to 2. Then all email with an SCL rating equal or greater than 5 will be Archived. All email with an SCL rating greater than 2, will be moved to the user’s Junk E-mail folder. You will want to experiment with the treshold settings. Note: every time you change the SCL rating, you will have to restart the Microsoft Exchange Information Store service.
Still in ESM, go to Servers > Servername > Protocols > SMTP, right click Intelligent Message Filtering Properties and enable the Default SMTP Virtual Server.
2. Download and install the IMF Archive Manager – go to http://www.gotdotnet.com/workspaces/workspace.aspx?id=e8728572-3a4e-425a-9b26-a3fda0d06fee
By default when IMF archives a message, it does not archive the SCL rating assigned to the message. To do so, create a registry key DWORD value, ArchiveSCL, and assign it a value of 1. Run RegEdit, and navigate to HKLM > SOFTWARE > Microsoft >Exchange, right-click ContentFilter, click New, and then click DWORD value.
Type ArchiveSCL for the registry key value. Right-click ArchiveSCL, and then click Modify. In Edit DWORD, under Value Data, type 1.
3. Configure Outlook to display the SCL rating.
Here a picture is worth a thousand words: http://www.smallbizserver.net/Default.aspx?PageContentID=12&tabid=174