Planning Network Port Requirements
When the first versions of Exchange came out, security was not a major consideration. Of course, security was of concern in 1996 but the level of Internet connectivity that systems have today, together with the threat posed by being connected to the Internet, make it quite different. Obviously, this has changed in recent years. Windows Firewall is now a main component of every Windows Server 2008 operating system. Windows Firewall basically filters inbound and outbound traffic based on firewall rules. Exchange Server 2010 creates the Windows Firewall rules to open the ports required during Exchange Setup—thus you no longer need to configure these settings manually.
Some companies want to put certain server roles ...