kb2593557 referenced in the 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.
We have a single domain with multiple GCs. The problem right now would appear to be affecting all users. The problem is new, things worked in the recent past. The only change that I can think of is I introduced a second mailbox/cas server and created a DAG. So I checked to see if any Outlook clients were connecting to this second server and perhaps the issues lied there somehow, but Get-Counter “\MSExchange RpcClientAccess\User Count” -ComputerName exserver1, exserver2 | ft as well as Get-Counter “\MSExchange OWA\Current Unique Users” -ComputerName exserver1, exserver2|ft show all connections are to exserver1 the primary server. As for the SELF object, it is present and has "Write Personal Information" right.
Not sure what else to check???