Mail service example

In this case, the new Internet Access (eth2) will be used for the mail service, including incoming and sending (port 25). This rules should by inserted:

1. Rule to masquerade the outgoing traffic for the eth2 interface;
   • Type: General configuration;
   • Rule: POSTROUTING;
   • Interface: eth2;
   • Protocol: ALL;
   • Module: Leave blank;
   • Source IP: Leave blank;
   • Origin port: Leave blank;
   • Destination IP: Leave blank;
   • Destination port: Leave blank;
   • Parameters: Leave blank;
   • Politics: SNAT;
   • Value: eth2 IP;

2. Rule that accepts incoming traffic for the port 25:
   • Type: General configuration;
   • Rule: INPUT;
   • Interface: eth2;
   • Protocol: TCP;
   • Module: Leave blank;
   • Source IP: Leave blank;
   • Origin port: Leave blank;
   • Destination IP: Leave blank;
   • Destination port: 25;
   • Parameters: Leave blank;
   • Politics: ACCEPT

3. Rule to allow the replies for port 25 by the Internet mail servers:
   • Type: General configuration;
   • Rule: INPUT;
   • Interface: eth2;
   • Protocol: TCP;
   • Module: Leave blank;
   • Source IP: Leave blank;
   • Origin port: 25;
   • Destination IP: Leave blank;
   • Destination port: Leave blank;
   • Parameters: ! --syn;
   • Politics: ACCEPT

4. Rules to forward outgoing Internet SMTP traffic for eth2
   • Type: General configuration;
   • Rule: OUTPUT;
   • Interface: eth1;
   • Protocol: TCP;
   • Module: Leave blank;
   • Source IP: eth1 IP;
   • Origin port: Leave blank;
   • Destination IP: ! eth1 IP;
   • Destination port: 25;
   • Parameters: Leave blank;
   • Politics: MARK;
   • Value: 1 (firewall tag);

5. Rules to forward outgoing SMTP traffic with origin in IPBrick for the new interface (eth2);
   • Type: General configuration;
   • Rule: OUTPUT;
   • Interface: eth1;
   • Protocol: TCP;
   • Module: Leave blank;
   • Source IP: eth2 IP;
   • Origin port: 25;
   • Destination IP: ! eth1 IP;
   • Destination port: Leave blank;
   • Parameters: Leave blank;
   • Politics: MARK;
   • Value: 1 (firewall tag);

6. Rule to forward traffic with origin in LAN and destination the port 25 in Internet (only when is used a external SMTP account)
   • Type: General configuration;
   • Rule: PREROUTING;
   • Interface: eth0;
   • Protocol: TCP;
   • Module: Leave blank;
   • Source IP: LAN IP;
   • Origin port: Leave blank;
   • Destination IP: ! eth1 IP;
   • Destination port: 25;
   • Parameters: Leave blank;
   • Politics: MARK;
   • Value: 1 (firewall tag);