I've read here and other places that it is important to use the FrontendTransport role when creating an Exchange 2013 Receive Connector for devices that will use the Exchange server for relay. If you don't use a FrontendTransport connector you will regularly have to stop and restart the Transport service.
My problem is when I create Receive Connector using the FrontendTransport role using port 25 (or any other port) I can't establish a connection to the server using that port. I'm using "telnet server 25" from another machine on the inside network for my testing.
Even my Internet Receive connector was created with the Hub Transport rule.
What must I do to get a FrontendTransport Receive connector to actually listen on port 25?