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Customizing Exchange Server Intelligent Message Filter

 

Topic Last Modified: 2007-01-22

You can customize the following configuration settings in Microsoft® Exchange Server Intelligent Message Filter:

  • Change the location of the archive directory.
  • Store the spam confidence level (SCL) rating when archiving messages. By default, Intelligent Message Filter does not save the SCL rating on messages that it archives.
  • Filter messages sent by authenticated users. By default, authenticated users bypass Intelligent Message Filter.

To customize these settings, you must create a registry key value under the following registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Exchange\ContentFilter 
CautionCaution:
Incorrectly editing the registry can cause serious problems that may require that you reinstall the operating system. Problems resulting from editing the registry incorrectly may not be able to be resolved. Before editing the registry, back up any valuable data.

Additionally, you can create a registry key to configure the maximum size of safe senders lists and blocked senders lists. For more information, see the section "Setting the Size of Spam Rules" later in this topic.

The archive location is the directory where Intelligent Message Filter saves filtered messages when you decide to archive messages marked as UCE that have a rating greater than the specified gateway threshold configured on the Connection Filtering tab in Message Delivery Properties. By default, messages are archived in \Exchsrvr\mailroot\vsi n\UCEArchive where n is the SMTP virtual server instance number. By default, the \Exchsrvr directory is created in the <drive letter>:\Program Files parent directory.

To change the location of the archive directory
  1. In Registry Editor (regedit), in the details pane, right-click ContentFilter, click New, and then click String value.

  2. Type ArchiveDir for the registry key value.

  3. Right-click ArchiveDir, and then click Modify.

  4. In Edit String, under Value Data, enter the full directory path where you want to archive messages filtered by Intelligent Message Filter. For example, type C:\Archive.

By default, when Intelligent Message Filter archives a message, it does not archive the SCL rating assigned to the message. If you want to archive the SCL rating together with the message, you can create a registry key DWORD value, ArchiveSCL, and assign it a value of 1.

To archive the SCL rating with archived messages
  1. In Registry Editor (regedit), right-click ContentFilter, click New, and then click DWORD value.

  2. Type ArchiveSCL for the registry key value.

  3. Right-click ArchiveSCL, and then click Modify.

  4. In Edit DWORD, under Value Data, type 1.

    When this registry key value is set to 1, Intelligent Message Filter saves the SCL rating with the archived messages. The SCL rating is persisted in the message as an extended message header (X-SCL).

    When this registry key is set to 0, or if the registry key value does not exist, Intelligent Message Filter archives the message, but does not save its associated SCL rating.

By default, Intelligent Message Filter only filters messages and assigns SCL ratings to messages sent through anonymous connections. Messages sent by authenticated users bypass Intelligent Message Filter. If you want Intelligent Message Filter to assign SCL ratings to messages sent by authenticated connections, create a registry key DWORD value, CheckAuthSessions, and assign it a value of 1.

To filter messages sent through authenticated connections
  1. In Registry Editor (regedit), right-click ContentFilter, click New, and then click DWORD value.

  2. Type CheckAuthSessions for the registry key value.

  3. Right-click CheckAuthSessions, and then click Modify.

  4. In Edit DWORD, under Value Data, type 1.

    When this registry key value is set to 1, Intelligent Message Filter filters messages sent by both authenticated and anonymous users.

    By default, Intelligent Message Filter only filters messages sent by anonymous users. When the CheckAuthSessions registry key value is set to 0, or if the registry key value does not exist, the default behavior applies.

The spam rule on a user's Inbox includes the user's safe senders list, blocked senders list, and Outlook metadata of approximately 300 bytes. By default, the size limit for a user's rule is 510 KB. This default size typically allows for approximately 2,000 entries in the safe senders and blocked senders lists.

Because the safe senders and blocked senders lists are synchronized between Outlook clients and the mailbox store, large lists can affect performance. You may want to reduce the size limit. Conversely, you may want to increase the size limit to allow users more flexibility in configuring the safe senders and blocked senders lists.

You can set a custom size limit for these rules by adding a new registry key value to the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\
noteNote:
You must enter the new size limit in bytes when you use this registry key.
To customize the size limit of a user's spam rule
  1. In Registry Editor (regedit), in the details pane, right-click System, click New, and then click DWORD value.

  2. Type Max Extended Rule Size for the registry key value.

  3. In Edit DWORD, under Value Data, enter the maximum size in bytes you want to allow for a user's spam rule.

 
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