Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!NNSC.NSF.NET!craig
From: craig@NNSC.NSF.NET (Craig Partridge)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Special way to query DNS?
Message-ID: <9007191911.AA13386@ucbvax.Berkeley.EDU>
Date: 19 Jul 90 11:45:35 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
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> I have a question that I haven't seen addressed anywhere.  I suspect that 
> the answer is NO but I'll ask anyway.
> 
> Dumb Question #79745:
>    Is there any way to query the Domain Name Server(s) to ask for ALL the 
> MX records pointing to a certain host?  For instance, my system may have several
> sites calling in via UUCP that it acts as MX forwarder for.  Is there any way
> I can query the DNS so that I can dynamically look up to see who has my system
> in their MX records?

No there isn't a handy way -- that's why RFC 974 says it is bad ettiquette
to list someone as an MX without asking them first.

It occurs to me that you might be able to generate such a list by doing an
inverse query to your local server.  Your server typically  (though not
always -- depends on configuration) will do an MX lookup on mail it
gets to help decide how to route the mail.  Thus it should pull MXs that
reference it into your local server cache (whether it gets all of them
in the cache at once depends on the e-mail patterns at your site).  An
inverse query might then catch the MXs.  [Mind you, I'd always thought
that IQ's were so useless that I no longer fully recall how to use them.
I think this is correct -- if not, someone please firmly correct me].

Craig