Microsoft KB Archive/151690

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XCLN: What is the 'Custom' Rule Action For?

Article ID: 151690

Article Last Modified on 1/19/2007


  • Microsoft Exchange Client 4.0
  • Microsoft Exchange Client 5.5
  • Microsoft Outlook 2000 Standard Edition
  • Microsoft Outlook 98 Standard Edition
  • Microsoft Outlook 97 Standard Edition
  • Microsoft Outlook 2002 Standard Edition

This article was previously published under Q151690


A Custom Rule Action is a DLL which contains code which may be called as a consequence of a rule firing. This article explains how to register a Custom Rule Action DLL so it is available as an option.


The Microsoft Exchange client for Windows has an option under Tools, Inbox Assistant, Add (or Edit) rule, called Custom. In Outlook, this dialog can be reached through the Rules Wizard, by selecting 'perform a custom action'. This dropdown box is typically blank unless custom rule dll's have been registered. A custom rule action can be created using the Microsoft Exchange Software Development Kit (SDK).

The custom dropdown option will use an entry in the registry under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Exchange\Client. Specifically, the Microsoft Exchange client is looking for a Custom Actions key that is not available by default. Under this key, corresponding values for a rule processing .DLL file are included (this .DLL is created using the SDK). The following example illustrates this using an example found in the SDK under the registry value used for the above key called Launch:


With the registry entry and rule processing .DLL correctly configured, the user can then check the custom option and select the name displayed (in this case, Launch) from dropdown list to customize Inbox rule processing for the Microsoft Exchange client.

A sample Custom Action agent, called CRARUN is available as part of the Exchange 5.5 SDK. See http:\\\downloads to obtain the SDK samples. Documentation is provided in the Platform SDK. See


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