Sendmail & IpTable Rules

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http://serverfault.com – I need to setup IpTable Rules for a server with nginx, ssh and sendmail. Now, the problem is, with my rules I can not send emails to other hosts anymore. Emails to localhost do work, but sending to different servers does not, when the firewall is up. I tried opening both Incoming and Outgoing Port 25 and DNS lookup ports, but nothing worked. Any ideas? Update: Here are my rules: #! /bin/sh # firewall iptable rules interface="eth0" # first, deny all iptables -P INPUT DROP iptables -P OUTPUT DROP iptables -P FORWARD DROP # open loopback device completely iptables -A INPUT -i lo -j ACCEPT (HowTos)