Adding Muliple Receive Connectors to an existing list

Hello,

I'm attempting to add about 10 IP's receive connectors to an already existing set of IP's. I understand that if I simply use set-receiveconnectors it will overwrite the existing list.

I attempted to follow the steps located here;

http://exchangeserverpro.com/how-to-add-remote-ip-addresses-to-existing-receive-connectors

using this script;

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$RecvConn = Get-ReceiveConnector "USFSM-S-CASHUB1\Internal ABB and FOPE"
$RecvConn.RemoteIPRanges += "10.5.2.3", "10.5.2.4", "172.16.5.2", "172.16.5.3", "192.168.6.4", "192.168.6.5"
Set-ReceiveConnector "Relay Connector" -RemoteIPRanges $RecvConn.RemoteIPRanges

But receive the following error;

Exception setting "RemoteIPRanges": "Cannot convert value "System.Object[]" to type "Microsoft.Exchange.Data.MultiValuedProperty`1[Microsoft.Exchange.Data.IPRange]". Error: "Faile
d to convert 192.168.6.5 from System.String to Microsoft.Exchange.Data.IPRange. Error: Error while converting string '192.168.6.5' to result type Microsoft.Exchange.Data.IPR
ange: The format of the IP address 192.168.6.5 is invalid. Example of a valid IP address: 192.168.1.10""
At line:1 char:11
+ $RecvConn. <<<< RemoteIPRanges += "10.5.2.3", "10.5.2.4", "172.16.5.2", "172.16.5.3", "192.168.6.4", "192.168.6.5"
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : PropertyAssignmentException

Does anyone have any ideas what I'm doing wrong?

Thanks