XIMS: Chat Service Returns List of All Users When WHO Command Is Sent Without Parameters

If you send the WHO command without any parameters to a Microsoft Exchange Chat Service computer, the server returns a list of all users, although the list may be truncated if it is very long.

This behavior is by design.

Some system administrators may want the server to return a blank list when the WHO command is sent without any parameters, rather than returning a list of all users.

This feature is available in the latest service pack for Exchange Server version 5.5. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The English version of this feature should have the following file attributes or later:

Component: Chat Service


This feature was first included in Exchange Server 5.5 Service Pack 3. After you obtain this feature, the server can be configured so that it returns a blank list when the WHO command is sent without any parameters. To do so, use the following steps.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

1. Start Registry Editor (Regedt32.exe).
2. Locate the following key in the registry:
   HKEY_LOCAL_MACHINE\Software\Microsoft\Exchange\ChatSvc\Parameters
3. On the Edit menu, click Add Value, and then add the following registry value:
   Value Name: RestrictWho
   Data Type: REG_DWORD
   Value: 1
4. Quit Registry Editor.