Great Circle Associates List-Managers
(May 2001)

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Subject: Re: problem
From: Tim Pierce <twp @ rootsweb . com>
Date: Fri, 4 May 2001 17:43:06 -0400
To: Sharon Tucci <sharon @ listhost . net>
Cc: List-Managers @ GreatCircle . COM
In-reply-to: <20010503182600 . GYQ28559 . tomts14-srv . bellnexxia . net @ b8q7201>; from sharon @ listhost . net on Thu, May 03, 2001 at 01:50:46PM -0400
References: <B712F7D8 . 8A24%chuqui @ plaidworks . com> <B712F7D8 . 8A24%chuqui @ plaidworks . com> <200105010655 . f416tpQ09099 @ linux . local> <20010503182600 . GYQ28559 . tomts14-srv . bellnexxia . net @ b8q7201>
User-agent: Mutt/1.2.5i

On Thu, May 03, 2001 at 01:50:46PM -0400, Sharon Tucci wrote:
> Many of the senators and staff have autoresponders that go 
> out when they receive email. Normally this isn't a problem,
> but instead of getting ONE copy of these autoresponders,
> we're getting sometimes 10 or 20 of them. (These are
> weekly and monthly newsletters, so there is no reason
> that this should happen and there is no looping taking
> place.... it will be one batch and then its done)

We occasionally get a complaint that someone has received dozens
or even hundreds of copies of a single mailing list message.
Each time we've been able to track down the source of the problem,
it's been a misconfigured gateway at the receiver's end, sort of
like this:

+------+                   +------------+        +------------+
| list | --- Internet ---> | receiver's | -----> | receiver's |
| host |                   |  gateway   |        | POP server |
+------+                   +------------+        +------------+

Your mailing list server sends a message to the receiver's site,
which is received by a big mail gateway in their network.  The
message is now out of your hands.  The gateway must now deliver
the message to, say, 50 users on an internal POP server.  Here's
where things can get sticky.

The gateway opens an SMTP connection with the internal POP server
and announces it has mail for 50 users.  Suppose one of those users
has a full mailbox.  The POP server will return a 450 response for
that user, meaning "can't deliver now, but try again later."

The gateway *should* recognize that it should only try redelivering
to that particular user.  Not all systems do recognize this.  Instead,
they forge ahead and deliver the mail to the other 49 recipients, and
then turn around and re-queue it for all 50.  In a few minutes it
redelivers the message to all 50, except for the one whose mailbox is
full.  So it re-queues the message again.  And so on.

We have not had this problem specifically with  However,
this always seems to be the cause of the problem when hundreds of
users of a single mailing list, all at the same site, all suddenly
report getting duplicate copies of list mail at the same time.

Indexed By Date Previous: Re: autoresponders and vacation notices (was: problem)
From: Sharon Tucci <sharon @ listhost . net>
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From: Tim Pierce <twp @ rootsweb . com>
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From: Sharon Tucci <sharon @ listhost . net>

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