qmail-amavisd is a small program (annother qmail-queue replacement) allowing to set up "one-and-half"-MTA amavisd scan.
I work with qmail for several years, mostly satisfied with it, however, lots of spam and viruses forced me to think of early rejection and more efficient scanning than spamc/spamd from mailfilter.
Amavis seemed to be The Right Thing, but...
qmail-scanner is unsuitable for any real mailserver. Running a perl script for each mail brings any hardware to the knees.
dual-MTA setup described somewhere on Amavis site is ugly (disclaimer: it is my personal opinion) and it will probabily not work with existing vpopmail setup.
helper-progs/amavis.c seems to be unfinished and it is totally undocumented.
So, I've recalled my C skills and put forth emacs.
The result is "one and half"-MTA setup. qmail-qsmtp.c forwards all incoming mail to 127.0.0.1:10024, logging amavis reply and possible internal errors. Address is hardcoded right now, I'll make it more configurable one day (see TODO).
Current version -- 0.94
0.94. I'll have to write down detailed description
Fixed coredump on empty envelope; still wonder how empty envelope can be received. Looks like some bug somewhere; however, so far it affected only spam.
Historical versions -- 0.91
Early rejection -- ability to reject viruses/spam during SMTP session
Fits nicely in qmail framework
Hight memory requirements for running a number of amavises
3-10 seconds delay on inbound mail for spam checking; users may complaint
Sometimes, qmail-queue.smtp receives empty envelope from qmail-smtpd. I don't understand how can it be; I couldn't reproduce this error, even with logged SMTP session. The problem seems to be persistent with some hosts; however, so far those hosts only sent SPAM.
Graph, something like mailgraph, but more qmail-oriented
Ability to pass mail from authenticated users without time-consuming amavisd check