Second instance of qmail

[albans]

Hi,
I wonder if it's possible to install a second instance of qmail in order to allow SMTP-AUTH with qgreylist... On a Fedora5, with PSA 8.1.1.

What I wanna do:
- use the standard qmail with RBL MAPS and qgreylist on port 25
- having another instance on (for example) port 525 which only allow authenticated users to send mail (authenticated users = pop3 account on the same host)

Any tips or how-to?
I just found this how-to:
http://forum.qmailrocks.org/showthread.php?t=2372&goto=nextoldest
Will it work with Plesk?

Thanks!