if [ "$1" == "start" ]; then
  #modprobe nfnetlink_queue
  iptables -A INPUT -p tcp -m tcp --dport 25 -m state --state NEW -j NFQUEUE --queue-num 23
fi

if [ "$1" == "stop" ]; then
  #modprobe -r nfnetlink_queue
  iptables -D INPUT -p tcp -m tcp --dport 25 -m state --state NEW -j NFQUEUE --queue-num 23
fi