How do I setup internal mail server?

Here is an example of hosting an internal mail server.

internal mail server ----- RF650VPN box ------- internet

mail server = 192.168.1.2 with domain name "test.com"
VPN lan = 192.168.1.1
VPN wan = 203.64.122.172

1) You need to register test.com so there is a MX record on the internet pointing the domain name to 203.64.122.172

2) Enable SMTP proxy in webadmin

3) Accepted incoming domain = test.com in webadmin

4) SMTP route = test.com --->192.168.1.2

5) Packet filter rules should be set according to your Organizational Security Policy.

The packet filter rules are entered according to the principle:
source IP - service - destination IP - action

minimum packet filter requirements for this are:
LAN mail server (source IP) - smtp (service) - destination mail server (destination IP) - allow (action)

If you already have "LAN - any - any - allow", no further packet filter rules are required for smtp proxy.

With the above setup, you can enable email virus scan protection.