nat () {
    # All traffic to $THIS_PORT on this container
    # will be redirected to $THAT_PORT on $THAT_IP
    $THAT_IP=$1
    THIS_PORT=$2
    THAT_PORT=$3

    # Accept forward incoming traffic
    iptables -I FORWARD -d $FWD_IP -m tcp -p tcp --dport $THAT_PORT -j ACCEPT

    # Accept forward return traffic
    iptables -I FORWARD -s $FWD_IP -m tcp -p tcp --sport $THAT_PORT -j ACCEPT

    # Redirect packets to remote
    iptables -t nat -I PREROUTING -m tcp -p tcp --dport $THIS_PORT -j DNAT --to-destination $THAT_IP:$THAT_PORT
}

NAT_IP=10.143.0.20
nat $NAT_IP 33 10013
nat $NAT_IP 993 10015
nat $NAT_IP 587 10016





# Include this line ONCE, at the end.
iptables -t nat -I POSTROUTING -d $FWD_IP -j MASQUERADE