SOA record confusion

[Kevin Darcy]

Compuman wrote:

>If you do a NS query for the domain coventry.gov.uk. it returns the
>nameservers for the domain.
>
>However, If I do nslookup -type=ns blahblahblah.coventry.gov.uk
>obviously, it doesnt return nameserver information because the domain
>doesnt exist. But it DOES return the SOA record.
>
>How is this possible? Why is there no NXDOMAIN error? How is the DNS
>configuration different so that it returns this information?
>
>Ive tried others eg blahblah.google.com, blahblah.yahoo.com - all give
>errors.
>
>Actually, even an  'A' record doesnt give any errors, e.g. nslookup
>abcdef.coventry.gov.uk.
>
coventry.gov.uk has a wildcard MX record, so it is returning NODATA (no 
data of requested type) to all queries. According to RFC 2308, Section 
6, they MUST return an SOA record in the Authority Section in such 
responses, but it is optional ("SHOULD") for them to return NS records 
in the Authority Section ("implicit referral"). The responses seem legal 
to me.
                                                                        
                                        - Kevin