Creating an addition receive connector on the Hub Transport servers
In order to not affect intra-org communication (aka Hub Transport server to Hub Transport server communication), we must create a new receive connector that listen on port 25/SMTP using the virtual IP address we specified when we created the NLB cluster. To do so launch the Exchange Management Console and then click Server Configuration followed by Hub Transport. Now select the first Hub Transport server in the result pane and then open the property page for the default <server> receive connector in the work pane as shown in Figure 2.1 below.
Figure 2.1: Opening the property page for the default <server> receive connector
Click the Network tab and configure the IP address to the internal non-cluster IP address (Figure 2.2).
Figure 2.2: Specifying a non-clustered IP address for the default <server> receive connector
Now create a new receive connector (type Custom) and name it Inbound SMTP relay (WNLB), then click Next (Figure 2.3).
Figure 2.3: Naming the new Receive WNLB receive connector
On the Local Network Settings page (Figure 2.4), configure the receive connector, so it only listens on port 25 on the NLB cluster address, which in the example is 10.10.1.194. Although optional, it’s also a good idea to enter a FQDN for the connector. Click Next.
Figure 2.4: Configuring the receive connector to listen on the virtual NLB cluster IP address
Now enter the IP addresses that should be allowed to relay through the receive connector. Make sure not to specify a ranger here, but only the specific IP addresses configured on the servers running the applications that must submit messages to the Exchange 2007 organization via this receive connector (Figure 2.5). Then click Next.
Figure 2.5: IP address that should be allowed to submit messages to this receive connector
Finally click New and then Finish to create the new receive connector (Figure 2.6).
Figure 2.6: Completion page
Now open the property page for the new receive connector, and then click the Permission Groups tab. Under the Permission Groups tab, tick Anonymous users and nothing else as shown in Figure 2.7.
Figure 2.7: Allowing anonymous users to submit message to the receive connector
Next we must grant the permissions required in order for the specified remote IP addresses to be able to relay through this receive connector. To do so, open the Exchange Management Shell and type the following command:
Get-ReceiveConnector "Inbound SMTP relay (WNLB)" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "ms-Exch-SMTP-Accept-Any-Recipient"
