Hello, My server is on FC3 (fedora3) eth0 is WAN ( dynamic IP ) eth1 is LAN This a continuation of my most recent post " smtp/pop and NAT only " . I have set the rules as follows : # Generated by iptables-save v1.2.11 on Wed May 11 11:06:56 2005 *nat :OUTPUT ACCEPT [0:0] :PREROUTING ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] -A POSTROUTING -o eth0 -s 192.168.0.0/24 -j MASQUERADE COMMIT # Completed on Wed May 11 11:06:56 2005 # Generated by iptables-save v1.2.11 on Wed May 11 11:06:56 2005 *mangle :PREROUTING ACCEPT [93:9058] :INPUT ACCEPT [85:8650] :FORWARD ACCEPT [8:408] :OUTPUT ACCEPT [88:8886] :POSTROUTING ACCEPT [95:9218] COMMIT # Completed on Wed May 11 11:06:56 2005 # Generated by iptables-save v1.2.11 on Wed May 11 11:06:56 2005 *filter :INPUT ACCEPT [85:8650] :FORWARD ACCEPT [8:408] :OUTPUT ACCEPT [87:8810] -P FORWARD DROP -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -i eth1 -o eth0 -s 192.168.0.248 -j ACCEPT -A FORWARD -i eth1 -o eth0 -s 192.168.0.253 -j ACCEPT -A FORWARD -i eth1 -o eth0 -p tcp --dport 25 -j ACCEPT -A FORWARD -i eth1 -o eth0 -p tcp --dport 110 -j ACCEPT COMMIT # Completed on Wed May 11 11:06:56 2005 The clients 192.168.0.248 / 253 are able browse and send/recieve mails. But other clients are not able to send/recieve mails. Here are fews things that I did: >From fedora3 server : [root@fedora3 ~]# cat /etc/resolv.conf ; generated by /sbin/dhclient-script search saice.edu nameserver 203.145.184.13 [root@fedora3 ~]# telnet 64.233.185.27 25 Trying 64.233.185.27... Connected to gsmtp185.google.com (64.233.185.27). Escape character is '^]'. 220 mx.gmail.com ESMTP g3si533838wra >From non NAT clients : [root@ ~]# cat /etc/resolv.conf nameserver 203.145.184.13 # ppp temp entry [root@ ~]# telnet 64.233.185.27 25 Trying 64.233.185.27... Connected to 64.233.185.27 (64.233.185.27). Escape character is '^]'. 220 mx.gmail.com ESMTP 35si1283118wra quit 221 2.0.0 mx.gmail.com closing connection Connection closed by foreign host. [root@ ~]# I am not able to ping ISP gateway or DNS. Non NAT are not able send/recieve mails. I don't understand why this FORWARD command does not work. Or have I forgotten something ? Can't we just use PREROUTING command for smtp and pop. Thanks in advance Varun