I am using Exchange2013 CU 5 on Win 2012 R2. I want to be able to control servers that can relay email to outside recipients. Before we had a Load Balancer, I would just add the IP of the servers to relay email to the Receive Connector and set the Authentication to Externally Secure. But we have purchased a Kemp VM Load Balancer. My testing found that, while keeping it Externally Secure, I had to add the IP of the Load Balancer into the Receive Connector or I could not relay email to outside from any of my servers. Further testing found all I needed in the receive connector was the External Secure and the one IP of the Load Balancer. This is easier but I can no longer limit the servers that can relay SMTP email to an outside recipient.
Can anyone tell me how to limit servers that can relay SMTP email to outside when using a Load Balancer?