We're running qmail/maildrop/qmail-scanner/spamd to filter spam, which is working fine. We direct spam to a special Maildir in each user's main Maildir. However, we still get a ton of spam sent to bogus or discontinued mailboxes here, and get stuck in the outgoing queue trying to bounce it back to a bogus reply address.

Right now, maildrop only filters email going to real mailboxes on our server. What I'd like to do is continue bouncing non-spam sent erroneously to bad addresses back to the sender, but redirect spam sent to bad email addresses to /dev/null, so that the outgoing queue is a manageable size. I'm not sure whether you'd do this from the global maildroprc, or from running spamc invoked by .qmail-default or the default pointing to a mailbox running a .mailfilter, or what the recipe should be. Currently the /etc/maildroprc just looks like this:

if ((/^X-Spam-Status:.*Yes/)) { to "./Maildir/.Spam/." }

Clues appreciated!