Unable to delete appointments as a delegate in Outlook 2010

While implementing Exchange 2010 SP1 and Microsoft Outlook 2010 I came across a bug in Outlook. When someone gives delegated access to their calendar, the delegate can add and modify appointments but not delete the appointments. The user receives this error; “Could not complete the deletion. The items may have been already deleted or moved. “.

 Let’s fist describe the scenario as when the issues arise.

One user (user1) has editor delegated rights to the mailbox of user2. If user1 makes an appointment in the calendar of user2 this will succeed. If user1 want to change the appointment, this will also succeed. When the user1 want to delete the appointment, the user will receive the following error: “Could not complete the deletion. The items may have been already deleted or moved. ” This scenario is on a Windows XPSP3 (fully patched) system with Microsoft Outlook 2010.

Deleting the appointment works fine in the following scenarios;

1. When the same user is logging into Outlook Web App, the user is allowed to delete the same appointment.
2. When the same user is logging into Microsoft Outlook 2007 on Windows XP, the user is allowed to delete the same appointment.
3. When the user is allowed to delete the same appointment Microsoft Outlook 2010 on Windows 7 the user is allowed to delete the same appointment.

First thoughts on this issue are, no rights issue because it works on OWA, Outlook 2007 and on Microsoft Outlook 2010 on Windows 7. After a lot of testing and trying things Microsoft Support came up with the following Knowledge Base article 202517 which describes a workaround for earlier versions of Outlook. It seems that when you want to delete an appointment as a delegate Outlook wants to move the message to the Deleted Items folder of the owners calendar. The delegate has no access to this folder so the delegate isn’t allowed to move the appointment to that folder.

The article describes two options, one is a registry change and the other one is a registry change and changing rights on the Sent Items folder. The registry key was not available.

Setting the DelegateWastebasketStyle in HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Options\General can be done with two values: 

• Setting DelegateWastebasketStyle to 8Option 8 should arrange that the deleted appointment is moved to the deleted item folder of the delegate. Unfortunately this option is not working for the current situation.
  
• Setting DelegateWastebasketStyle to 4 plus changing the rights on the Deleted Items folder to at least Author.Option 4 is working but this is in my opinion a workaround which is not easy to implement since the user need to assign different rights.

Setting DelegateWastebasketStyle to 8 should be a good solution but unfortunately it’s not working. Using the second option is a workaround but nothing more than that.

Nevertheless it is still strange that it is working with the scenarios as described above. I’ll keep you up to date since the support case is still open. 😉

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