My qmail is already setup, it can send and get email at the stage.
And it can be telent from other machine to get normal response.

I would like to setup the qmail as a relay for my company,
let say company domain is: onepiece.com and my ISP domain is:
twopiece.com

How can I set the qmail accept all emails "from twopiece.com" and all
emails "to onepiece.com"?
How to relay all the emails in qmail relay to another server, let say
domain: mypiece.com?
How can I setup the SMTP AUTH? Do I use the qmail-smtpd-auth?

Thanks a lot.