> I would like to know how can I filter the mail relay received > in my port 25 with the firewall,.. I want only accept the > packets from only one ip, my ISP. iptables -P INPUT DROP # Maybe you don't need it, but I'll add it anyway iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A INPUT -i <eth_inet> -s <isp_mailserver_ip> -p tcp --dport 25 -j ACCEPT However, this way you will be blocking *everything* else from coming in. You probably want to accept local traffic, something like this : iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -i <eth_lan> -s <net_lan> -j ACCEPT If you're running other servers on the box too (e.g. a webserver), you also need rules for those servers. Or you could do simply this, dropping all traffic *not* coming from your isp's mailserver : iptables -A INPUT -i <eth_inet> -s <! isp_mailserver_ip> -p tcp --dport 25 -j DROP Rob
