input output forward drop 收发邮件规则怎么写

Question

$IPT -P FORWARD DROP
$IPT -A FORWARD -i $INF -o $EXT -p tcp -m multiport --ports $DNS_PORT,$SMTP_PORT,$SSMTP_PORT,$IMAPS_PORT,$POP3_PORT,$POP3S_POR
T -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

$IPT -A FORWARD -i $EXT -o $INF -p tcp -m multiport --ports $DNS_PORT,$SMTP_PORT,$SSMTP_PORT,$IMAPS_PORT,$POP3_PORT,$POP3S_POR
T -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

$IPT -A FORWARD -i $INF -o $EXT -p udp -m multiport --ports $DNS_PORT,$SMTP_PORT,$SSMTP_PORT,$IMAPS_PORT,$POP3_PORT,$POP3S_POR
T -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

$IPT -A FORWARD -i $EXT -o $INF -p udp -m multiport --ports $DNS_PORT,$SMTP_PORT,$SSMTP_PORT,$IMAPS_PORT,$POP3_PORT,$POP3S_POR
T -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
不行