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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 ( or or Level 3's DNS server ( if you're email server is configured to use 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: