SpamControl is a collection of patches for qmail developed and maintained
by Erwin Hoffmann (feh@fehcom.de).

Some SpamControl features: smtp-auth (plain, login and cram-md5),
requirement of brackets on addresses, qmail-queue, bigtodo, moreipme,
recipients, STARTTLS...

WWW: http://www.fehcom.de/qmail/spamcontrol.html