Outlook delegates and categories: Why you need Owner permissions on the user’s calendar

Recently I had an interesting issue related to a delegate scenario in conjunction with categories:

A delegate was not able use categories in a shared mailbox. It was just greyed out. I knew you need to have at least Reviewer permissions on the shared folder in order to work with categories. So I thought that would be an easy one and I was going to tell them how to fix this…..but before I checked the folder’s permissions and realized that the delegate had Publishing Editor assigned.

After some testing we decided to grant Owner permission, but the delegate were still not able to work with categories.

Why was it still not working, even with Owner permissions?

I’ve found a matching KB article for my issue:

You cannot change a user’s categories when you work as a delegate in Outlook

After reading the article careful multiple times, I found a hint:

Therefore, if you are working in any shared folder of another user’s mailbox, you must have at least Reviewer permissions to the other user’s Calendar folder to view and apply the other user’s categories, and Owner permissions to create new categories, or delete existing categories for any shared folder in the other user’s mailbox.

It must has to do with the permissions on the Calendar folder. But when I checked this folder ther user had already Publishing Editor like on the other folders.

The solution

In the end it all came down to the permissions on the Calendar. The delegate needs to have Owner permissions on the folder in order to get the full functionality for categories. On all other folders Reviewer is sufficient for categories.

Why Calendar?

The list of color categories in a mailbox is stored in a hidden message in the Calendar folder of a mailbox.

You can find all categories in a property of a FAI:

Open the mailbox with MFCMAPI and open the associated contents table of the calendar folder


Then sort by Message Class and look for an item with the class IPM.Configuration.CategoryList


You will find all the categories in the property PR_ROAMING_XMLSTREAM



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