shell script plugin response control

[The A. <arc...@gm...>]

I am trying to employ a valid user checking mechanism that can drop
connections when a user does not exist and get all the damn double bounces
out of my email. the qmail-spp patch went in just fine, and I grabbed the
valid user check plugin script (http://www.maiers.de/qmail/art38,72.html).

Testing shows that it works, exiting 0 or 1 as appropriate, but how do I
translate that 0 or 1 into action on the part of qmail-spp? When testing via
manual smtp mailing, I can verify that the script runs, but it doesn't do
anything with the result and qmail continues to accept the connection
despite no user existing.

There are no commands for spp inside the plugin (Rmesg is what I'm after),
and looking at other plugin shell scripts they don't have it either. So what
am I missing?