From ucspi-tcp read about tcpserver and tcprules. If you want to setup POP3 access then you should read through checkpassword documentation. Extract qmail source code with the following. If the hostname is not given or given wrong then qmail will simply refuse to accept mail for your server. Next qmail aliases for the system need to be setup.
Aliases are a powerful system of mail delivery in qmail.
You can setup aliases or pseudonyms for users. All email directed to those email addresses can be redirected to a existing local user or forwarded to an external mail address. The .qmail-newbie file contains the delivery instruction for user newbie. Each address or user needs to be on a seperate line. Postmaster - This will be the mail administrator for your system so this file needs to be carry the name of the mail administrator of your system.