"The Delegates settings were not saved correctly" error when you try to add a delegate in Outlook

KB Article: https://support.microsoft.com/kb/2593557

INTRODUCTION

When you use Microsoft Outlook to add or to remove a delegate, the delegate is not added or deleted. Additionally, you receive the following error message:

The Delegates settings were not saved correctly. Unable to activate send-on-behalf-of list. You do not have sufficient permission to perform this operation on this object.