Deleting the Hidden Delegate Rule in Outlook

Here's my problem: When User A sends a meeting request to User B, three other users also receive the request. In the past, these three users were delegates for User B, but User B's mailbox no longer shows any delegates under the Tools, Options, Delegates tab. How can I stop Outlook or Exchange from forwarding User B's meeting requests to the other three users?

Outlook doesn't have a quick fix, but Microsoft recently released a tool that helps you troubleshoot problems with messages being forwarded to "phantom" delegates. You can download the Microsoft Exchange Server MAPI Editor for free from During the download, you'll be asked to specify where you want to place the extracted files. After the files have been extracted, go to the location you specified and you'll see that the executable is named mfcmapi.exe. This is a new version of a tool that has been around for a long time, but is now fully supported instead of just being some great Messaging API (MAPI) sample code.

Before you use the MAPI Editor, you need to know three things that happen when a user grants access to a delegate:

  • The delegate acquires Send on Behalf of permission for the user's mailbox.
  • Outlook updates the ACLs for individual mailbox folders with the permissions that were set for the delegate on the Delegates tab.
  • Outlook creates a hidden rule in the user's Inbox to forward incoming meeting and task requests and responses to the delegate.

It's the hidden rule that appears to be causing your problem. The simplest solution is to delete the hidden rule. The mfcmapi.doc file included with the MAPI Editor download contains complete instructions on how to use the tool and delete the delegate rule.

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