just go to this link
www.qmailrocks.org
In this link u will find that , it has documentation for all Linux flavours but not SUSE,
Just follow the RED HAT doc given in this site for SUSE,i.e doc for REDHAT & SUSE are same
Just follow REDHAT doc for SUSE , u will def able to install QMAIL on SUSE ,
AS I have configured it on SUSE 9.2 recently
Cheers
Gaurav
i