Re: [ietf-smtp] parsing SMTP replies

Hector Santos <> Tue, 23 March 2021 15:46 UTC

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Date: Tue, 23 Mar 2021 11:45:54 -0400
From: Hector Santos <>
Organization: Santronics Software, Inc.
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Subject: Re: [ietf-smtp] parsing SMTP replies
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On 3/22/2021 2:23 PM, John C Klensin wrote:
> Ned, Laura,
> Just a thought, based on little thinking and less information:
> Are there any plausible circumstances in which a system might
> want to encourage rolling up a few MXs but not very many?  If
> so, that would turn it into a limit, rather than requiring a
> separate announcement keyword.  I'm having trouble imagining
> such a case, so, if the answer is "no", don't bother with a
> detailed explanation.   However, because I think there is value
> in minimizing the number of announcements, the question seems
> worth asking.

If I may ....

If you are referring to situations similar to where private domains 
are being hosting by a 3rd party vendors or even a free ESP network,  
i.e. hosted by Yahoo's MX or  by Microsoft MX's, 
etc, yes, it has created a delivery problem.  The Outbound Queuing 
Strategies (OQS) need to be adjusted/sorted by MX (and thus IP).  A 
rule that may say: "My-Special-Customer.Com gets sending priority over" no longer applies when the special customer has decided to 
be hosted by

Hector Santos,