Re: [ietf-smtp] parsing SMTP replies

[Hector Santos <[e-mail]>]

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. private-domain.com 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 
gmail.com" no longer applies when the special customer has decided to 
be hosted by gmail.com.

-- 
Hector Santos,
https://secure.santronics.com
https://twitter.com/hectorsantos