Newbie Question: Is anyone actually using the Null MX (RFC 7505)?

Fri Feb 26 22:37:30 UTC 2021

In article <CAKaVjbP2KyB5FGtzAqYjnaagg4P7+E+32d+2HFZnLTVUz7kphw at mail.gmail.com> you write:
>1. Is there anyone actively using this Null MX? If so, may I please see
>that actual record line (in BIND zone file format) just to satisfy myself
>that I wrote mine correctly?

Yes.

services.net.   3600    IN      MX      0 .

>2. Which one makes more sense from the practical point-of-view: having a
>Null MX Record for the no-mail domain, or having no MX record at all?

Null MX of course.  See section 4 of RFC 7505.

Large mail systems like gmail and recent versions of mail servers like Postfix
all recognize a null MX.  I suppose there are some dusty old mail systems
that do something odd with it and throw an error message but so what?  You
don't want them to send you mail in the first place.

R's,
John