Enable DNSBL service in Postfix to reduce spam

You can enable additional DNSBL services in Postfix to reduce spam. We use zen.spamhaus.org for example below.

• Open Postfix config file /etc/postfix/main.cf or /usr/local/etc/postfix/main.cf (on FreeBSD), append reject_rbl_client zen.spamhaus.org to parameter smtpd_recipient_restrictions. Final setting looks like below:

smtpd_recipient_restrictions = ..., reject_unauth_destination, reject_rbl_client zen.spamhaus.org

It must be placed after reject_unauth_destination. You can add more DNSBL services after reject_unauth_destination, and they will be queried in the specified order.

• Restart or reload Postfix service is required.

References

• Postfix Configuration Parameters: reject_rbl_client

• Spamhaus website

  • Spamhaus DNSBL Usage Terms

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