Outlook Delegates issues
If you aren't familiar with the Outlook Delegates functionality, it provides you with the ability to specify a Delegate for your Mailbox. Delegates can perform items such as sending items on your behalf, and responding the meeting requests, etc. When you add a delegate, you can specify that they receive copies of your meeting requests, which is quite typical.

Now, say you have a few delegates, and one of them leaves the company. Your IT staff diligently deletes the account (and mailbox). However, all of a sudden, meeting requests to you now generate an NDR. The cause? Delegates. For whatever reason, Outlook stores delegates separately (they are actually stored as a hidden rule on your mailbox), so that if you delete a user account that was set as a delegate, Outlook doesn't automatically remove that delegate. Ok - this is easily fixed. You need to go into Outlook, Tools, Options, Delegates, and remove the non-existent user.

What if you've already done that, and nothing shows up in the Delegates tab?
http://support.microsoft.com/kb/253557/en-us comes to the rescue. The KB article talks about a little different situation, but one that applies nonetheless. The problem is that this "hidden" rule has become stranded. You can't see it (with Outlook), but it's still there, and still functioning. The solution is to use the Mdbview utility to log on to your mailbox. If you've never used mdbview before, a word of caution is that the output is pretty ugly! Anyways, after logging on to your mailbox, the instructions have you go to your inbox and find the message that has Schedule + EMS Interface in the description, and then delete that message. Normally, this should remove the delegation, but you still want to go back into your Outlook settings and check. In some cases, you may now see an Unknown account in the delegation, at which point you can remove it.
- posted by Ben Winzenz @ 3:34 PM