You should not use the list that was here any more.  It's not maintained.

You should not use Qmail any more.  It's not maintained, either.
Many of the patches at qmail.org aren't maintained.  It's as if
NCSA refused to cooperate with the Apache organization when it was
getting started.  Apache worked because NCSA was okay with it.
The current Qmail+patches doesn't work because DJB isn't on board.

You can patch Qmail for the checkuser problem, but it isn't Qmail any more.
You can look for a patch for the large queue DoS problem.
You can try to patch the no multiple RCPT TOs problem.
But it would be easier to migrate to a well-maintained MTA.
I recommend Postfix.

You can try to use the rblsmtpd that comes with ucspi-tcp.
We started getting wrong answers from it (false postives and negatives)
when our .cdb file reached 10 MB.  I recommend rbldnsd instead.

Tcpserver is still a good program.  Use it instead of inetd for
services that don't have a workable daemon mode of their own.
Or try xinetd.