how to integrate mail server [INACTIVE]

[lolex]

Hello,
I use BFW 31.10 on a network with 40 computers, 192.168.1.0/24
For Internet we have only one public IP address from ISP.
I want on a Ubuntu linux to install a mail server, but I ask how to make this with BFW. Where to place the mail server, in DMZ ? because is only one public address. And if somebody know what mail server on linux is simple to configure, I found many mail servers:postfix,qmail....but all are very dificult to configure for a beginner, and for 40 computers maybe is not necessary.
Many thanks

[lolex]

A good link
http://ubuntuforums.org/showthread.php?t=1189531