iptables forwarding to inside firewall

[Hanasaki JiJi <hanasaki@hanaden.com>]

Working on running a SMTP server inside the firewall that takes incoming 
SMTP traffic from outside the firewall.  The below rules are not 
working.  The firewall refuses connections.  Any input on what wrong?

Thanks,

internal mailserver = 192.168.1.2



#$PROG -t nat -A PREROUTING -i $NIC_EXTERNAL -p tcp \
        #-s 0/0 \
        #--dport smtp -j DNAT --to-destination 192.168.1.2:25

#$PROG -A FORWARD -i $NIC_EXTERNAL -s 0/0 \
        #-o $NIC_INTERNAL -d 192.168.1.2 -p tcp --dport smtp \
        #-m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

#$PROG -A FORWARD -i $NIC_INTERNAL -s 192.168.1.2 \
        #-o $NIC_EXTERNAL -d 0/0 -p tcp \
        #-m state --state ESTABLISHED,RELATED -j ACCEPT