Use this handy script to find objects in Active Directory that have inheritance disabled. This can be a good troubleshooting tool if you’re encountering this error at the end of a mailbox migration:

Warning: Unable to update Active Directory information for the source mailbox at the end of the move. Error details: An error occurred while updating a user object after the move operation.
–> Active Directory operation failed on casserver.domain.com. This error is not retriable. Additional information: Insufficient access rights to perform the operation.
Active directory response: 00002098: SecErr: DSID-03150BB9, problem 4003 (INSUFF_ACCESS_RIGHTS), data 0
–> The user has insufficient access rights.