Mail Server an Firewall rules

Gentlemen, good morning.
Please, I wonder if to set an external e-mail server it is necessary to enable rules in the firewall, or they are already pre-defined, the email service does not send or receive messages outside the local network.

1 - VMware ESXi with two physical interfaces, however only one is possible to access, green LAN 10.0.69.x virtualizing an NS 7.2 (alpha) using the two interfaces, a green LAN 10.0.69.x and other internet network red DHCP. The external DNS is configured as ZoneEdit (Dynamic DNS) and responding smoothly.

I ask the help of you because I’m beginner NS and I lack the necessary experience to perform such a configuration.

Thanks a lot for your attention, help and patience. See you.

They’re already pre-defined, but you should configure properly your gateway to permit NethService receives e-mails, for instance creating a new port forwarding rule on port 25

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