HI, Running a NLB 2 node setup. I'm trying to find out why some clients can connect trough mapi and some not. I'm suspecting one of the CAS server having trouble in the NLB setup. SO i ran: PS] C:\Windows\system32>Test-OutlookConnectivity -RpcProxyTestType:Internal -RpcTestType:Array WARNING: An unexpected error has occurred and a Watson dump is being generated: Object reference not set to an instance It happens on both CAS server. Can anyone clarify this up? Thanks of an object. Object reference not set to an instance of an object. + CategoryInfo : NotSpecified: (:) [Test-OutlookConnectivity], NullReferenceException + FullyQualifiedErrorId : System.NullReferenceException,Microsoft.Exchange.Monitoring.TestOutlookConnectivityTaskIvan

Have you created a Client Access Array? Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."