I've got a NAT firewall setup. I don't want to poke a hole for 7025 on the external address so I need postfix to talk to 7025 on either the internal address or localhost. I tried disabling Enable DNS lookups and adding my mail server host as 127.0.0.1 in /etc/hosts. However, now when I try to email an external domain is tries contact the IP of the server's A record rather than the MX record. What am I doing wrong?