VS: Dumb Question is an A or AAAA record required?
jukka.pakkanen at qnet.fi
Thu Jul 9 14:38:38 UTC 2020
Many spammers send in addition to MX to A records, if available. Still, it is a good practice to not to publish an A record for the mail zone, if not specifically needed for something else. Of course if it points to somewhere else than the receiving SMTP server, not much harm done mail-traffic-wise.
Lähettäjä: bind-users <bind-users-bounces at lists.isc.org> Puolesta Matthew Richardson
Lähetetty: 9. heinäkuuta 2020 16:06
Vastaanottaja: bind-users <bind-users at lists.isc.org>
Aihe: Re: Dumb Question is an A or AAAA record required?
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.
Do people think that this problem could still occur these days? What sort of transient (presumably DNS) failure might cause an SMTP server to deliver to A rather than MX?
>From: Anand Buddhdev <anandb at ripe.net>
>To: "@lbutlr" <kremels at kreme.com>, bind-users
><bind-users at lists.isc.org>
>Date: Thu, 9 Jul 2020 14:43:04 +0200
>Subject: Re: Dumb Question is an A or AAAA record required?
>On 09/07/2020 14:21, @lbutlr wrote:
>> Given a domain that is hosted and used for email and web, is an A
>> record for that domain actually required?
>It's not *required*. But see below.
>> That is, if bob.tld is hosted by example.com can you simply have
>> NS ns1.example.com
>> NS ns2.example.com
>> MX mx.example.com
>> www CNAME www.example.com
>> Without specifying
>> A 18.104.22.1684
>These days, many folk try to reach websites by typing just the bare
>domain name without the "www" prefix.
>If a user types "bob.tld" into a browser, the browser will issue an
>address lookup for "bob.tld", causing the resolver to ask for A and
>AAAA records for "bob.tld". If you don't have an A record at the zone
>apex, the browser will not get back any address and display an error
>message for the user. An alert user might try "www.bob.tld" but most
>users are likely to just give up.
>So while it's not *required* to have an address record at the apex,
>it's good practice to have one.
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