Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!ncrlnk!ncrcae!hubcap!gatech!uflorida!ukma!cwjcc!hal!ncoast!allbery
From: allbery@ncoast.UUCP (Brandon S. Allbery)
Newsgroups: comp.mail.sendmail
Subject: Re: Overlaying smail and mx-sendmail?
Message-ID: <12671@ncoast.UUCP>
Date: 12 Oct 88 22:52:19 GMT
Article-I.D.: ncoast.12671
References: <8602@shamash.UUCP> <810@ncar.ucar.edu>
Reply-To: allbery@ncoast.UUCP (Brandon S. Allbery)
Followup-To: comp.mail.sendmail
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 34

As quoted from <810@ncar.ucar.edu> by woods@ncar.ucar.edu (Greg Woods):
+---------------
| ....to which several people responded with the answer that you can tack a dot
| onto the end of the address, pass it through the resolver via the $[ $] 
| canonical name lookup feature, and check for the presence or absence of the
| dot afterwards to indicate resolver success or failure. When  Paul Vixie first
| pointed this out to me, I was quite excited about the possibility of having
| the best of both worlds. However, when I implemented it I discovered a very
| serious problem with doing this. Namely, if your name server returns a
| temporary failure, the message will bounce if the domain in the address is
| not in the UUCP maps (which is happening more and more often these days as
| Internet-connected sites begin depending more and more on the resolver
| and less and less on static tables like UUCP maps, as well they should).
+---------------

It seems to me that if the mailer depends on a network service like a name
server, and the name server returns a non-permanent error, sendmail's proper
response should be to queue the message and retry until either the server
comes back up or the message has waited for some configurable time; i.e. the
response to the nameserver being down should be the same as the destination
system returning a *temporary* error condition upon actual delivery.

Something for the folks working on the IDA pathalias lookup to consider:  the
same thing should happen if the pathalias database is in the process of
being rebuilt.

Or am I missing something?

++Brandon
-- 
Brandon S Allbery uunet!hal.cwru.edu!ncoast!allbery allbery%ncoast@hal.cwru.edu
(LAST RESORT ONLY:  allbery@uunet.uu.net)			DELPHI: ALLBERY
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