I am running Exchange 2013 on svr2013. I can send and receive mail locally, I can send externally, but I cannot receive mails from outside the company.
My static IP was coming from a DIA / VPN connections provided by the telco. As per test on the analyzer, port 25 cannot be reached or not listening. Although the port was opened already via the custom inbound setup. Another this is that, I am running also our website on the same static IP, and hosted on a Linux webserver. As I talked with the telco, they told me that they are not blocking port 25 on their side.