see > http://www.postfix.org

• reducing backscatter > http://www.postfix.org/BACKSCATTER_README.html
• postgrey
• http://www.debian-administration.org/articles/168
• http://isg.ee.ethz.ch/tools/postgrey/

check auto-whitelisted sites

# perl /usr/share/doc/postgrey/postgrey_clients_dump

reports

# cat /var/log/mail.log | postgreyreport --nosingle_line --check_sender=mx,a  --show_tries \ --separate_by_subnet=":=============================================================================================\n")