Active Directory operation failed on server.domain.local. This error is not retriable. Additional information: Access is denied.Active directory response: 00000005: SecErr: DSID-03152492, problem 4003 (INSUFF_ACCESS_RIGHTS), data0 + CategoryInfo : WriteError: (0:Int32) [Add-ADPermission], ADOperationException + FullyQualifiedErrorId : 3E19955E,Microsoft.Exchange.Management.RecipientTasks.AddADPermission
The Add-ADPermissions Powershell command is also checking for the correct permissions of the Microsoft Exchange Server group in addition to the permissions of the account running the command.
The minimum required permissions of the Microsoft Exchange Server group is assigned by default to the domain, but inheritance has been disabled on those permissions. Enable inheritance for the Microsoft Exchange Server group, and make sure those permissions propagate down to all child objects.
Add-ADPermission -Identity mailbox_name -User domain\user_name
-AccessRights ExtendedRight -ExtendedRights "send as"
where: