Re: [Asrg] What are the IPs that sends mail for a domain?

Alessandro Vesely <vesely@tana.it> Sun, 21 June 2009 06:10 UTC

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Date: Sun, 21 Jun 2009 08:11:10 +0200
From: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [Asrg] What are the IPs that sends mail for a domain?
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David Nicol wrote:
> On Sat, Jun 20, 2009 at 2:20 PM, Alessandro Vesely<vesely@tana.it> wrote:
>> However, in practice one needs an email address to do any legitimate use of
>> SMTP, and hence a domain is required.
> 
> There isn't any technical reason why MUA software can't do its own
> delivery with today's technology.  The whole concept of "outbound MTA"
> seems like a throwback.

I'd agree that the reasons why we needed outbound MTAs then, and why 
we need'em now are completely different. However, I'd still call the 
current reason "technical"; in facts, its origin is likely related 
with overcoming the former reason.

> With the exception of delivery delays, but
> having a MUA attempt its own delivery and then switch to the smarthost
> on connection or other temporary failure wouldn't require any
> inspiration.

(W.r.t. Steve's terminology / architecture comment, I understand "MUA" 
above as a conceptually personal host, e.g. a laptop running mutt and 
exim.) Being suspicious about their ESPs, those users may prefer to 
deliver directly whenever possible. That is the only reason I see for 
attempting a direct delivery first, and it is a largely suboptimal 
solution anyway (e.g. it provides no reliable storage for sent messages.)

Some people even run MTAs on dynamically assigned IPs. At any rate, 
they use an email address featuring a domain (that they possibly own.) 
That is the domain we should use to work out responsibility.

> As if web-service MUAs are going to fade away, which is doubtful.

They won't go away, but they are fine, since they require proper 
authentication. They relay via submission servers that possibly run on 
the same host or LAN.