[CentOS] Apparent BIND problem doing RBL lookups for Postfix

[listserv.traffic at sloop.net]

> On Wed, 2010-04-14 at 17:36 -0700, listserv.traffic at sloop.net wrote:
>> --
>> Problem:
>> Postfix is doing RBL lookups on zen.spamhaus.org.
>> Everything goes along groovy - but then lookups start failing.
>> 
> Does your network interface show any abnormalities - dropped packets
> etc? I assume you have no local ratelimiting (via iptables etc)?

No rate limiting, and ifconfig isn't showing any
errors/drops/overruns etc.

-Greg