Mailing with Postfix to other domains

[radec94]

So i'm having some troubles with Postfix on an Ubuntu Server 12.04, the thing is that i need Postfix to send and recive mails from domains other appart from mine. In fact, i just want it to work with the other domain on the other server on my own network. We are having 2 servers, each one with his own domain and they are both on the same network (172.16.9.20 and 172.16.3.20). I belive i need to configure the parameter "mynetworks" or "mydestinations" and something related with the "relay_hosts"
but i'm not sure.

Thanks for the help.

PD: Sorry for my english, it's not my main language.

[falko]

So you want server2 to send through server1 without authentication? Just add server2's IP to mynetworks (/etc/postfix/main.cf) on server1, and add server1's hostname to relayhost (/etc/postfix/main.cf as well) on server2. Restart Postfix on both servers.