Re: The need for specifying the OFFICIAL domain name in a header

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#31

From: Rob Austein
Date: Fri, 10 Apr 1992 00:48

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   Date: 10 Apr 92 03:16:29 GMT
   From: kyle@uunet.uu.net (Kyle Jones)

   Not quite.  If CNAME's were allowed for mail then you'd have to
   do an extra lookup.  One lookup to map the aliases to the
   canonical name, and another lookup for any MX records for the
   canonical name.

Bzzzz.  Sorry, Kyle.

CNAME lookup is completely transparent.  Your DNS resolver should do
it for you on the fly.  Ie, you look for the MX RR and if the name is
really a CNAME you get back both the CNAME and the MX RR to which the
CNAME points.  Eg, given RRs:

    MISKATONIC-CTHULHU.ARPA.  IN  CNAME  CTHULHU.MISKATONIC.EDU.
    CTHULHU.MISKATONIC.EDU.   IN  MX   1 CTHULHU.MISKATONIC.EDU.
    CTHULHU.MISKATONIC.EDU.   IN  A      256.6.6.6

a single query for the triple <MISKATONIC-CTHULHU.ARPA, IN, MX> should
get you all three RRs.  Please see RFCs 1034 and 1035 for details.

--Rob Austein <sra@asylum.sf.ca.us>

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References: <1992Apr8.164249.10851@husc3.harvard.edu> <1992Apr10.031629.26764@uunet.uu.net>

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Path: arc1-ca.pugleaf.net!sparky!uunet!cs.utexas.edu!qt.cs.utexas.edu!news.Brown.EDU!noc.near.net!asylum!sra
From: sra@epilogue.com (Rob Austein)
Newsgroups: comp.mail.headers
Subject: Re: The need for specifying the OFFICIAL domain name in a header
Message-ID: <SRA.92Apr10014819@asylum.epilogue.com>
Date: 10 Apr 92 00:48:19 GMT
References: <1992Apr8.164249.10851@husc3.harvard.edu> <1992Apr10.031629.26764@uunet.uu.net>
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Organization: Epilogue Technology Corporation
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In-reply-to: kyle@uunet.uu.net's message of 10 Apr 92 03:16:29 GMT

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