Restrict Mailbox to One Mobile Device

Hi,

I am trying to restrict Mailbox to one Mobile Device, I ran the following commands

Get-MobileDeviceStatistics -Mailbox:"Test.Mail2" |fl DeviceID

Set-CASMailbox -Identity: "Test.Mail2" -ActiveSyncAllowedDeviceIDs: "xxxxxxxxxxxxx"

Both commands ran succefully , If i am not wrong now Active sync for this mailbox should be configured on above specific Mobile device with ID "xxxxxxxxxxxxxxxxx"

But i can configure this mailbox on multiple devices. How can i restrict to

Regards
Usman Ghani

Usman Ghani - MCITP Exchange 2010