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How to Enable and Configure the Spam Confidence Level Thresholds

 

Applies to: Exchange Server 2007 SP3, Exchange Server 2007 SP2, Exchange Server 2007 SP1, Exchange Server 2007

Topic Last Modified: 2006-09-18

This topic explains how to use the Exchange Management Console or the Exchange Management Shell to enable and configure the spam confidence level (SCL) thresholds. The SCL threshold is the value at which a particular message is identified as potential spam and is acted on. The Content Filter agent is the last filter to scan inbound messages. Therefore, the settings of the SCL thresholds and threshold actions are very important. If you set the SCL thresholds too high, you may not reduce the spam that enters your organization. If you set the SCL thresholds too low, the risk is that you will filter messages from legitimate users.

You can enable and set each SCL threshold action to a value between 0 and 9, where 0 is considered less likely to be spam, and 9 is considered more likely to be spam.

noteNote:
After you configure the SCL threshold actions, you should periodically monitor these settings and adjust them based on your organization's needs.

You enable and set the SCL thresholds and corresponding actions as follows:

  • Delete messages that have a SCL rating greater than or equal to   This option deletes the message but does not inform the sending server of the deletion. In fact, the computer that has the Edge Transport server role installed sends a fake "OK" Simple Mail Transfer Protocol (SMTP) command to the sending server and then deletes the message. Because the sending server assumes that the message was sent, the sending server does not retry to send the message in the same session.
  • Reject messages that have a SCL rating greater than or equal to   This option rejects the message and sends an SMTP error response to the sending server.
  • Quarantine messages that have a SCL rating greater than or equal to   This option quarantines the message and sends it to the spam quarantine mailbox that you specified. For more information about how to configure the spam quarantine mailbox, see How to Specify a Spam Quarantine Mailbox.
    importantImportant:
    By the nature of the feature, the IT administrator who is responsible for the spam quarantine mailbox can view potentially private and sensitive messages and send mail on behalf of anybody in the Exchange organization.

You can enable and configure the SCL thresholds and SCL threshold actions to work together. When you enable multiple SCL threshold actions to work together, consider the following requirements:

  • The SCL reject threshold must be greater than the SCL quarantine threshold.
  • The SCL delete threshold must be greater than the SCL reject threshold and the SCL quarantine threshold.

To perform the following procedures on a computer that has the Edge Transport server role installed, you must log on by using an account that is a member of the local Administrators group on that computer.

Also, before you perform these procedures, confirm the following:

  1. In the Exchange Management Console, click Edge Transport.

  2. In the work pane, click the Anti-spam tab, and then select Content Filtering.

  3. In the action pane, click Properties.

  4. Click the Action tab, and select the check box for the actions that you want to enable.

  5. Set the SCL thresholds for the corresponding actions.

  6. Click OK to save your changes and close the dialog box, or click Apply to save your changes without closing the dialog box.

  • To enable the SCL reject action and configure the SCL reject threshold, run the following command:

    Set-ContentFilterConfig -SCLRejectEnabled <$true | $false> -SCLRejectThreshold <Int32>
    

    For example, to reject messages that have an SCL rating of 8 or more, run the following command:

    Set-ContentFilterConfig -SCLRejectEnabled $true -SCLRejectThreshold 8
    
  • To enable the SCL delete action and configure the SCL delete threshold, run the following command:

    Set-ContentFilterConfig -SCLDeleteEnabled <$true | $false> -SCLDeleteThreshold <Int32>
    

    For example, to delete messages that have an SCL rating of 9 or more, run the following command:

    Set-ContentFilterConfig -SCLDeleteEnabled $true -SCLDeleteThreshold 9
    
  • To enable the SCL quarantine action and configure the SCL quarantine threshold, run the following command:

    Set-ContentFilterConfig -SCLQuarantineEnabled <$true | $false> -SCLQuarantineThreshold <Int32>
    

    For example, to send messages that have an SCL rating of 7 or more to the spam quarantine mailbox, run the following command:

    Set-ContentFilterConfig -SCLQuarantineEnabled $true -SCLQuarantineThreshold 7
    

For detailed syntax and parameter information, see Set-ContentFilterConfig.

To ensure that you are reading the most up-to-date information and to find additional Exchange Server 2007 documentation, visit the Exchange Server TechCenter.
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