4-E: Greylisting
This is a very good way to lower the incoming spam.
I'll use a modified version of JMS greylisting program I got from here -> http://www.brandonturner.net/blog/2009/08/qmail-ipv6-jgreylist/
It's very simple to use and it covers all basics. If you need something more advanced, go to the site and read how the config is done.
wget http://www.bltweb.net/qmail/jgreylist-0.8-ipv6.tar.gz
tar -xzf jgreylist-0.8-ipv6.tacd
jgreylist-0.8-ipv6r.gz
make
make install
nano /etc/services/qmail-smtpd/run
#add this before the "if"s part starts
================================================
# greylisting
JGREYLIST_DIR="/var/qmail/jgreylist/"; export JGREYLIST_DIR
====================================
#and then add
/var/qmail/bin/jgreylist \
#right after
exec /usr/bin/softlimit -m 256000000 \
/usr/bin/tcpserver \
-v -R -l "$LOCAL" -x /etc/tcp.smtp.cdb \
-c "$MAXSMTPD" \
-u "$QMAILDUID" -g "$NOFILESGID" 0 smtp \
#and before
/var/qmail/bin/qmail-smtpd mail.example.com \
/home/vpopmail/bin/vchkpw /usr/bin/true 2>&1
#remember not to leave empty spaces or comments.
#NOW SAVE AND EXIT.
#restart qmail and everything should work now. if not, check the smtp logs.