Postfix is a widely used mail transfer agent. Integrating DNSBL checks significantly reduces spam before it reaches your mail queue.
Why Use DNSBL with Postfix?
DNS-based blocklists allow Postfix to reject mail from known spam sources during the SMTP connection, before accepting the message.
This approach saves bandwidth, storage, and processing resources by stopping spam at the door.
Configuring DNSBL Rejection
Add DNSBL checks to your smtpd_recipient_restrictions:
main.cf configuration:
smtpd_recipient_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_rbl_client bl.fraudcache.com,
permit
Client Access Lists
For local blocklists, use client access restrictions:
Client access configuration:
smtpd_client_restrictions = check_client_access hash:/etc/postfix/client_access
Best Practices
- Use Multiple Blocklists - Layer DNSBLs with content filtering for defense in depth
- Test Mode First - Log rejections before blocking to identify false positives
- Whitelist Critical Senders - Allow trusted partners to bypass blocklist checks
Configure Fraudcache DNSBL
Learn how to integrate our DNSBL service with your mail server.