This is a bit rough yet.  Sorry.

WARNING: I have been using a system like this one for about two months with
good success.  However, this code if somewhat different than what I am
currently using and hasn't get been well tested.  Be careful.

Install the spambayes package.  Create a new qmail user "qmailf" that is
in the group "qmail".  Setup the filter directory:

	$ umask 022
	$ mkdir /var/qmail/filter
	$ cd /var/qmail/filter
	$ mkdir info messages
	$ mkfifo input
	$ mkfifo status
	$ chown -R qmailf.qmail .
	$ chmod g+w input

Train a DB:
	$ <spambayes>/mailsort.py -t -d wordprobs.cdb ham.mbox spam.mbox

Create a whitelist (you should add hosts that legitimately forward mail
to you):

	$ touch whitelist.txt

Run qspambayes.py as qmailf as a daemon.  Patch qmail-queue.c and replace
/var/qmail/bin/qmail-queue with patched version.  If qspambayes.py dies then
qmail-queue will hang until it is restarted.  whitelist.txt and wordprobs.cdb
can be replaced without stopping qspambayes.py (e.g. make a new version and
move it in place).

You can use show_delayed.py to view messages that have been temporarily
rejected.