Dumb Question is an A or AAAA record required?

Matthew Richardson matthew-l at itconsult.co.uk
Thu Jul 9 16:03:01 UTC 2020

My question is raised because of such "poor decisions" by certain web
hosting providers (naming no names!) whose provisioning systems require
records for both www and the domain root pointing to their systems, and
where those systems DO LISTEN on port 25.

In these modern days, should one be concerned about this for a domain where
the MX records point to proper enterprise grade email services?  The
problem is that the web hosting provider's poor decision might interfere
with the enterprise email system.

I think Matus may be correct that this is only an issue if the MX query
returns NODATA rather than timing out.  In the old days (10-15 years ago),
I think a timeout may have triggered the failback from MX to A, but I am
not sure.

Best wishes,

>From: Anand Buddhdev <anandb at ripe.net>
>To: Matthew Richardson <matthew-l at itconsult.co.uk>, bind-users <bind-users at lists.isc.org>
>Date: Thu, 9 Jul 2020 17:06:13 +0200
>Subject: Re: Dumb Question is an A or AAAA record required?

>On 09/07/2020 16:06, Matthew Richardson wrote:
>> On a related issues there were (perhaps long ago) issues if the A record
>> for a domain had an SMTP server on it, where email could sometimes be
>> delivered to that A record rather than the MX.  I had (again long ago:
>> 10-15 years) actually seen this occur.
>Note that *delivery* will only happen if that A record were actually 
>listening on tcp/25 and accepting SMTP connections. No-one should be 
>opening up the SMTP port on a server meant to serve only HTTP(S) 
>traffic. Anyone who does that deserves what they get for making such 
>poor decisions.

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