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Spamhaus ZEN Failed by Google and Level 3

posted May 18, 2011, 8:54 AM by Jeremy Walker   [ updated May 18, 2011, 9:18 AM ]
Do not forward DNS queries to Google's DNS servers (8.8.8.8 or 8.8.4.4) or Level 3's DNS server (4.2.2.1) if you're email server is configured to use zen.spamhaus.org for DNSBL (Block List Provider). Our servers were configured in this way and every DNSBL query for known bad IP addresses would not match.

I set our DNS server to forward to our ISP's DNS servers instead. Now it works beautifully and my boss is happy.

My co-worker found a forum post that confirmed my findings:

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