Config advice

Hi

I haven't touched my qpsmtpd setup for years, but I'm moving it and want 
to upgrade now. So I seek advice for how to setup the current qpsmtpd.
What I want:

qpsmtpd receives all mail to my domains.
the local users will use qpsmtpd as a smtp server.

This means that the local users will log in with some flavor of auth, 
probably vpopmail_sql. Currently I use flat_file for testing.

So far so good. It's the further processing where I'm in doubt. Mail 
from outside mustn't be relayed, whereas my users of course have to send 
to other hosts. Also, spam checking should only be for incoming mail, 
not for my users.

In my existing setup I forward to postfix on another port. Not sure if 
that is necessary or desirable any longer. I see there is a 
postfix-queue plugin. It fails with permission errors when I try it, and 
I want to check here before I spend too much time going in the wrong 
direction.