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List:       nanog
Subject:    Re: Newbie Question: Is anyone actually using the Null MX (RFC 7505)?
From:       Grant Taylor via NANOG <nanog () nanog ! org>
Date:       2021-02-26 22:51:46
Message-ID: 771451b4-ffe3-0bb7-5b72-4b3fa5510aea () spamtrap ! tnetconsulting ! net
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On 2/26/21 12:10 PM, borg@uu3.net wrote:
> Hmm right... Somehow I tought that having that special Null MX will 
> silently discard message... I dont know why...

It's Friday.  I'm presuming that many of us have had a long week and are 
ready for the weekend.  ;-)

> So, RFC 7505 is pretty much even pointless in my opinion.

No, it's not pointless.  See Alan's reply to my previous message for why 
a Null MX helps as a sender / MSA operator.

See point #2 in my previous message for why you care about Null MX as a 
receiver.

> You have to do more.. to pretty much achieve the same.

But it's not the same.

You cause hard failures fast.  It means that sending servers should 
never contact the A / AAAA addresses, much less every time the sending 
system retries to send.  So you do save yourself some CPU cycles as a 
recipient.

> Its just easier to not having MX on subdomains that does not serve 
> as email destinations.. Less records in DNS.

Easier has seldom been better.

If you publish a Null MX for said subdomain(s), my server will give up 
immediately.  If you don't publish a Null MX, my server will pester your 
A / AAAA IPs every four hours for days at a time.



-- 
Grant. . . .
unix || die


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