How to set 2 qmail servers in the same domain

[Origoni, Maurizio]

Hi !
I have a qmail mail server with tcpserver and it works fine. Now I want to
setup a second qmail server to use for secondary MX in my domains. How can I
allign the 2  mail servers so if the first server go down the second accepts
mails for my customers in automatic mode ? When the first goes up again, the
second sends to it the mail received automatically ?
Thanks :-))