Exchange – Trying to get list of all users with mobile devices.

I’m running Exchange 2010 SP3.

I’m trying to make an export that will tell me what users in my origanization are using active sync, and how perhaps have many devices they have.

I would imagine an easy way of achiving it, would be:
Get-Mailbox -server “servername” | Get-ActiveSyncDeviceStatistics | ft DeviceType, DeviceUserAgent, LastSuccessSync
but it does not seem to work.

All I get is errors saying
The ActiveSyncDevice domain01\users\Tim cannot be found
+ CategoryInfo : NotSpecified: (991:Int32) [Get-ActiveSyncDeviceStatistics], ManagementObjectNotFoundException
+ FullyQualifiedErrorId : 81D1A14,Microsoft.Exchange.Management.Tasks.GetMobileDeviceStatistics

Even though this user does have a mobile device …. does anyone have some good advice or idea ?