Softfail is an enhaced greylisting system to be used on qmail MTA patched
with SMTPEXTFORK feature. It is an independent program, which is forked from
qmail-smtpd. It allows manual whitelisting and blacklisting as well as
automatic black and whitelisting. Automatic whitelisting is done by the usual
greylisting method while automatic blacklisting is done when the remote SMTP
server breaks some aspects of RFC rules and insists on redelivery very early.

All aspects of softfail's behavior can be configured. There are maintainance
scripts to be ran from crontab, which removes expired entries and generates
reports.

WWW:	http://www6.freebsdbrasil.com.br/~eksffa/l/dev/qmail-smtpextfork/