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Re: Proposed change for RFC0974

1998-11-06 07:59:40
On Fri, 06 Nov 1998 22:18:45 +1100, you said:
Forgive the question, but whats the difference between an IP that is down 
because of lets say Scheduled Network-Maintenance _and_ an offline host ?
Perhaps I am wrong but to all intents they appear the same, yes ?

Well, for *one* delivery, they appear the same.  The distinction is on
the long-term differences.  The machine I'm posting this from handles a
fair amount of mail per day (500+ items a day or more).  Now, if one
recipient host does down for a backup for 30 minutes, my machine will just
re-queue and re-try later.  However, many machines I send mail to are
*chronically* unavailable (to the point where a retry-every-30-mins
strategy still times out after 5 days).

Now, it just so happens that many of these offending sites don't HAVE
MX entries, so we attempt delivery to their A record.  I think the point
that was being made was that if they *had* MX entries with a backup at
their ISP, that they couldn't use ETRN to suck down their mail unless my
machine properly handled rollover to the backup MX entry, because their
machine wouldn't know to ETRN to mine, only to the ISP's server.

Are there, in fact, any systems with significant market share that manage
to get MX record handling wrong?

                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                Virginia Tech

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