netnews@uafhp.uark.edu (Netnews) (07/18/90)
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?
Thanks!
- David Summers
(dws@uafsun4.uark.edu)pvm@VENERA.ISI.EDU (Paul Mockapetris) (07/19/90)
There is no general method for finding out where a particular piece of information is to be found. For specific cases, say finding host names given addresses, the DNS builds indicies. paul
craig@NNSC.NSF.NET (Craig Partridge) (07/19/90)
> 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
barmar@think.com (Barry Margolin) (07/20/90)
In article <4940@uafhp.uark.edu> netnews@uafhp.uark.edu (Netnews) writes: > Is there any way to query the Domain Name Server(s) to ask for ALL the >MX records pointing to a certain host? No. You would have to query every domain server in the world in order to do this, since there's no inherent restriction on who can have MX records pointing to a host. There's nothing stopping a domain in Australia from pointing an MX record to my workstation in Massachusetts. -- Barry Margolin, Thinking Machines Corp. barmar@think.com {uunet,harvard}!think!barmar
del@thrush.mlb.semi.harris.com (Don Lewis) (07/26/90)
In article <9007250151.AA22673@cs.brown.edu> jb@CS.BROWN.EDU (Jim Bloom) writes: >I have threatened to remove the support for inverse queries from BIND. >There are lots of bugs in the handling of inverse queries since they >haven't been used since in-addr.arpa was created. Actually, until recently >nslookup used them until I told the author that incorrect answers were >being returned for 127.0.0.1 (loopback interface on BSD based systems) >when the server handled multiple zones. > > Jim Nslookup also barfs if the inverse query fails. Is this new version of nslookup available yet? I have a fairly recent version and it still appears to do inverse queries. -- Don "Truck" Lewis Harris Semiconductor Internet: del@mlb.semi.harris.com PO Box 883 MS 62A-028 Phone: (407) 729-5205 Melbourne, FL 32901