Exchange 2010 Set-ReceiveConnector -remoteIPRanges AdminLimitExceededException

I need to add approx 2000 IP addresses to our Exchange 2010 Receive connectors for internal servers (we dont allow desktops etc to connect to SMTP relays), but there are Scanner\coppiers and legacy windows and Unix hosts around the country on the same LAN's as workstations that need access.

Is there a limit I can increase in AD to allow this to work from Powershell ? I seem to get to about 1280 or so entries before powershell gives up - but I can still add then 1 by one from the GUI.
(multiple servers with that need identical configuration!)

Example below: ( just to show the error)

[PS] D:\>$recvCnn = Get-ReceiveConnector "Dummy"
[PS] D:\>$recvCnn.RemoteIPRanges = "127.0.0.1"
[PS] D:\>Set-ReceiveConnector "Dummy" -RemoteIPRanges $recvCnn.RemoteIPRanges
[PS] D:\>Get-Content .\SMTPACL.txt | foreach { $recvCnn.RemoteIPRanges += "$_"}
[PS] D:\>Set-ReceiveConnector "Dummy" -RemoteIPRanges $recvCnn.RemoteIPRanges
The administrative limit for this request was exceeded.
    + CategoryInfo          : NotSpecified: (0:Int32) [Set-ReceiveConnector], AdminLimitExceededException
    + FullyQualifiedErrorId : A8F6FF3A,Microsoft.Exchange.Management.SystemConfigurationTasks.SetReceiveConnector

Any suggestions ???