Here’s something to be aware of if you’re running a Postfix (or possibly any mailserver), use Spamhaus, and are considering or have switched to Google DNS:
1. Spamhaus has banned Google Public DNS resolver queries. I didn’t know this until today. If Postfix is using Google Public DNS resolvers, rbl queries to zen.spamhaus.org fail but Postfix (Debian Lenny 2.5.5-1.1) logs NOTHING about it. Not the query attempt, not the failure, zilch, nut’n.
For more info, read the thread at:
via SOLVED: rbl check being skipped – Postfix logs no error on NXDOMAIN, do.