Setting up the mailer on Ubuntu?

Hello!

I can not understand how to configure a mail server on Ubuntu Server 10.04.

Configuration:
Ubuntu with ISPconfig 3 (is Postfix with Courier);

Internet connection through a router, all ports of the server are online;

the server is assigned a domain(let it be conditional, my-domain.name) through freedns.afraid.org.


What settings should be for a domain, and what to do c Postfixso I can send mail using sendmail in php scripts?

I can't find the manual, which would describe the entire configuration process.

If there is one — poke in the link, but I couldn't find.