Monitoring IIS 6 SMTP Server on Windows Server 2012R2

We are trying to monitor the RemoteQueueLength in WMI for IIS6 SMTP on Windows Server 2012R2. PRTG returns the following from running a batch file calling the 64bit version of Powershell. We did try just running it under the native 32bit Powershell that PRTG utilizes still.

C:\Windows\system32>C:\Windows\system32\WindowsPowerShell\v1.0\powershell.exe -file "C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXEXML\checkSMTPQueue.ps1" 
Get-WmiObject : Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESS
DENIED))
At C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXEXML\checkSMTPQ
ueue.ps1:3 char:28
+ $SMTPObject = Get-WmiObject <<<<  -Query "SELECT RemoteQueueLength,MessageSen
dRetries,NDRsGenerated,OutboundConnectionsRefused,OutboundConnectionsTotal,Remo
teRetryQueueLength,TotalMessagesSubmitted from Win32_PerfRawData_SMTPSVC_SMTPSe
rver Where Name='_Total'" -ComputerName server01a
    + CategoryInfo          : NotSpecified: (:) [Get-WmiObject], UnauthorizedA 
   ccessException
    + FullyQualifiedErrorId : System.UnauthorizedAccessException,Microsoft.Pow 
   erShell.Commands.GetWmiObjectCommand
 
<prtg>
<result><channel>RemoteQueueLength</channel><value></value></result>
</prtg>

From the 64bit powershell command line, it works:

PS>  Get-WmiObject -Query "SELECT RemoteQueueLength from Win32_PerfRawData_SMTPSVC_SMTPSe
rver Where Name ='_Total'" -ComputerName server01a


__GENUS           : 2
__CLASS           : Win32_PerfRawData_SMTPSVC_SMTPServer
__SUPERCLASS      :
__DYNASTY         :
__RELPATH         :
__PROPERTY_COUNT  : 1
__DERIVATION      : {}
__SERVER          :
__NAMESPACE       :
__PATH            :
RemoteQueueLength : 0

From the 32bit powershell command line, it fails:

PS C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXEXML> Get-WmiObject -Query "SELECT RemoteQueueLength from Win32_PerfRawData_SMTPSVC_SMTPServer Where Name ='_Total'" -ComputerName server01
Get-WmiObject : Invalid class
At line:1 char:14
+ Get-WmiObject <<<<  -Query "SELECT RemoteQueueLength from Win32_PerfRawData_SMTPSVC_SMTPServer Where Name ='_Total'" -ComputerName v-smtp-02a
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], ManagementException
    + FullyQualifiedErrorId : GetWMIManagementException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

Any thoughts on how to get PRTG to monitor queue info? Have we simply over thought it and there is a simpler solution?

SELECT RemoteQueueLength from Win32_PerfRawData_SMTPSVC_SMTPServer Where Name ='_Total'