domain lookup results

[Barry Margolin]

In article <slrn8jnjgt.8u4.phil at niko.cmc.ca>,
Phil Steinke <phil at niko.cmc.ca> wrote:
>I'm curious about how BIND looks up domain entries.  I'm trying to do "A"
>queries on domains that don't have IP's associated with them (such as
>cadence.com or synopsys.com) as part of an email anti-spam setup.  Some DNS
>servers will return "No address (A) records available for cadence.com",
>which I consider to be the correct response.  However, others will return
>"Non-existent host/domain", which would cause any mail from that domain to
>be rejected.

It sounds like you're using NSLOOKUP for your lookups.  Don't do that,
since it produces ambiguous output and different output for equivalent
responses.  It reports "Non-existent host/domain" even when the name exists
but doesn't have any records of the requested type.

I suspect it reports "No address records" when the remote server is running
a version of BIND that puts the SOA record in the response that indicates
that the requested entry doesn't exist, but "Non-existent host/domain" when
it just returns an empty response.

I suggest you use dig rather than nslookup.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
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