Postfix spam prevention by use of blacklists.

I switched my hosting servers to Centos 7 a couple years ago, my postfix instance has been a fun experiment for the past year or so.

Below see the instance of “Blocked using” in my maillog file.  The dips are when I was not using any, and the peaks are when I was using one, or many blacklist providers.   I’ve heard good things about the barracuda blacklist, so I’ll add that eventually, and watch for spikes.

Important parts of my main.cf

smtpd_recipient_restrictions =
permit_sasl_authenticated,
permit_mynetworks,
check_recipient_access mysql:/etc/postfix/mysql-virtual_recipient.cf,
reject_unauth_destination,
reject_invalid_hostname,
reject_non_fqdn_hostname,
reject_non_fqdn_sender,
reject_non_fqdn_recipient,
reject_unknown_sender_domain,
reject_unknown_recipient_domain,
reject_rbl_client bl.spamcop.net,
reject_rbl_client sbl.spamhaus.org,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client dul.dnsbl.sorbs.net,
permit