iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 25 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 143 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 993 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 110 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 783 -j ACCEPT
iptables -A INPUT -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -i eth0 -p icmp -j ACCEPT

iptables -A OUTPUT -m tcp -p tcp --dport 80 -j ACCEPT
iptables -A OUTPUT -m tcp -p tcp --dport 25 -j ACCEPT
iptables -A OUTPUT -m tcp -p tcp --dport 143 -j ACCEPT
iptables -A OUTPUT -m tcp -p tcp --dport 993 -j ACCEPT
iptables -A OUTPUT -m tcp -p tcp --dport 110 -j ACCEPT
iptables -A OUTPUT -m tcp -p tcp --dport 783 -j ACCEPT
iptables -A OUTPUT -d 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -m state -p icmp --state INVALID -j DROP