PostScreen

Postscreen Configurations:

postscreen_dnsbl_threshold = 2
# commented out the following to remove b.barracuda* as it denies access without subscription or something. trying without barracuda.
#postscreen_dnsbl_sites = zen.spamhaus.org*2, bl.spamcop.net*1, b.barracudacentral.org*1
postscreen_dnsbl_sites = zen.spamhaus.org*2, bl.spamcop.net*1, b.barracudacentral.org*1
postscreen_dnsbl_action = enforce
postscreen_greet_action = enforce
#postscreen_pipelining_enable = yes
#postscreen_non_smtp_command_enable = yes
#postscreen_bare_newline_enable = yes

Sample Log:

Nov  3 17:25:09 mx2 postfix/postscreen[5830]: CONNECT from [221.208.90.134]:19716 to [*]:25
Nov  3 17:25:09 mx2 postfix/dnsblog[5833]: addr 221.208.90.134 listed by domain zen.spamhaus.org as 127.0.0.3
Nov  3 17:25:09 mx2 postfix/dnsblog[5833]: addr 221.208.90.134 listed by domain zen.spamhaus.org as 127.0.0.11
Nov  3 17:25:09 mx2 postfix/dnsblog[5831]: addr 221.208.90.134 listed by domain b.barracudacentral.org as 127.0.0.2
Nov  3 17:25:15 mx2 postfix/postscreen[5830]: DNSBL rank 3 for [221.208.90.134]:19716
Nov  3 17:25:15 mx2 postfix/postscreen[5830]: NOQUEUE: reject: RCPT from [221.208.90.134]:19716: 550 5.7.1 Service unavailable; client [221.208.90.134] blocked using zen.spamhaus.org; from=<jonellemacfarland@lasqdev.com>, to=<hostmaster@*>, proto=ESMTP, helo=<lasqdev.com>
Nov  3 17:25:16 mx2 postfix/postscreen[5830]: DISCONNECT [221.208.90.134]:19716