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Re: Advanced tricks I use to get rid of spam using MX 4xx

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Subject: Re: Advanced tricks I use to get rid of spam using MX 4xx
From: Charles Cazabon <qmail@discworld.dyndns.org>
Date: Mon, 27 Nov 2006 14:07:52 -0600
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Jason Frisvold <xenophage0@gmail.com> wrote:
> On 11/27/06, Marc Perkel <marc@perkel.com> wrote:
> > No - on my system a 4xx error only means that that particular server isn't
> > ready. It means try the other servers or come back later. It certianly dos
> > not mean that all the servers aren't ready. That's what I use EXIM and not
> > Qmail. All other MTAs except Qmail behave this way. it's what the spec
> > says.  Qmail does it wrong.
> 
> Hrm..  I find this interesting and slightly disturbing.
[...]
> I'm not sure I like the idea of a mail server immediately trying another MX
> if the initial one it contacted was busy.  This just creates additional load
> on the other MXs and can cause additional meltdown.  I believe the "correct"
> way for this to work is to queue the message when a 4XX is received and
> retry later.

That is correct.  Any MTA which immediately tries another delivery upon
receiving a temporary deferral is broken.

Charles
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Charles Cazabon                               <qmail@discworld.dyndns.org>
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