Linux Mail Server Setup and Howto Guide

Hi Guys!

Please… if can you help me? 

I would like to configure two mail servers: one as Gateway server  and Interna serverl, over Centos 5.5 x64. 

I read http://www.linuxmail.info/post…..p-gateway/ it's OK, but I have  doubts:

- How should be the follows archives in Gateway server an Internal Server?

 /etc/hosts,  /etc/resolv.conf

 - Is necessary  Internet access on Internal Server?

- Is the hostname Gateway server indifferent? or this should be equals to hostname in my public records DNS?

- ¿where  should I configure the DNS server? in Gateway server or Internal Server and how should be the dns records? 

MX 5 —–> Internal or Gateway?

Mx 10 ——> Gateway or Internal?

- INTERNAL SERVER

2. Edit the file /etc/postfix/transport and add the lines below.

example.com    :                        -----> What means this? why is not smtp?
.example.com   :
*              smtp:[192.168.3.2]

I hope that you can guide me!

Thanks a lot!

Edward