RBL – Fight SPAM With Postfix

Using RBL is really efficient and pretty lightweight. All it take is some DNS queries and if you were going to receive a lot of spam email from the same client, this DNS entries will be cached in your (local) DNS. To get some figures on how many emails get caught through, on a server that 90% of the email rejected, 90 – 95% of them are from Realtime Blackhole Lists, the rest is relay being denied!

Configure Realtime Blackhole Lists (RBL) to Postfix

Edit /etc/postfix/main.cf file and edit the smtpd_recipient_restrictions entry to add a line’s:

    # Realtime Blackhole Lists
    reject_rbl_client xxxxxxxxxxxxxxxxxxxxxxxxx.srbl.malware.expert

Postfix smtpd_recipient_restrictions configuration should look something like this now:

smtpd_recipient_restrictions =
    warn_if_reject reject_non_fqdn_helo_hostname
    warn_if_reject reject_unknown_helo_hostname
    warn_if_reject reject_unknown_reverse_client_hostname
    # Realtime Blackhole Lists
    reject_rbl_client xxxxxxxxxxxxxxxxxxxxxxxxx.srbl.malware.expert

Where xxxxxxxxxxxxxxxxxxxxxxxxx.srbl.malware.expert is your subscription with key.

Restart Postfix

# /etc/init.d/postfix restart

More Blacklists

DNS Blacklist services

Sign up Now and Try SRBL Blacklist

You can now test SRBL Database list for FREE now 1 months! If they are not working as expected or you just want to cancel the subscription, you can do so anytime!

Sign Up NOW!