Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!triceratops.cis.ohio-state.edu!karl
From: karl@triceratops.cis.ohio-state.edu (Karl Kleinpaste)
Newsgroups: comp.mail.sendmail
Subject: Re: Unknown Host Error
Message-ID: <19567@tut.cis.ohio-state.edu>
Date: 9 Aug 88 14:07:41 GMT
References: <277@hal.UUCP> <5951@orstcs.CS.ORST.EDU>
Sender: news@tut.cis.ohio-state.edu
Lines: 20
In-reply-to: hakanson@mist.cs.orst.edu's message of 9 Aug 88 00:15:26 GMT

hakanson@mist.cs.orst.edu writes:
   >I do not understand how named and sendmail can resolve the name AND the
   >host still be UNKNOWN!

   This rather surprising behavior can occur when (for example) someone has
   an MX record pointing to an unknown host.

It can also happen if there is inconsistent data among a domain's
various nameservers out there.  In the last several months, I have
caught 3 or 4 instances where mail to some.site.domain got bounced
with `host unknown,' but when I later made a fast check for the host,
I got valid A or MX records.  On checking ALL of the nameservers for
the given host, 2 out of 3 had the correct data, the 3rd gave me an
authoritative denial of existence.  Oops.  Can you guess on which
nameserver my machine managed to have a grip when that mail was trying
to go through?

I generally try to duplicate the inconsistency in a typescript that I
can then send to the person identified in the SOA record.

--Karl