My reply had one typo. This is the fixed version.
When a client connects from 127.0.0.2, the Postfix DNSBL client
will make a query, for example, for 2.0.0.127.zen.spamhaus.org.
2.0.0.127.zen.spamhaus.org has address 127.0.0.4
2.0.0.127.zen.spamhaus.org has address 127.0.0.10
2.0.0.127.zen.spamhaus.org has address 127.0.0.2
That can be used to trigger a reject when the client sends mail.
The only glitch is that by default,
telnet 127.0.0.2 smtp
results in
Jul 1 17:09:57 wzv postfix/smtpd[13454]: connect from localhost[127.0.0.1]
But that is easily fixed with "ifconfig lo 127.0.0.2 netmask 255.0.0.0".
Jul 1 17:11:24 wzv postfix/smtpd[13454]: connect from unknown[127.0.0.2]
QED. Now, if the OP were only willing to cooperate he could have
had his answer hours ago.
Wietse
