Null MX records

The IETF appears to have had a draft to specify a null mx record whereby a domain would not handle mail and mail delivery systems would fail and return a undeliverable system immediately by directing a domain's only MX record to '.' (c/f https://datatracker.ietf.org/doc/html/draft-delany-nullmx-00)

Is this draft specification followed by most mail servers out there and worth setting up? Alternately, what's the best way to configure mail to not be delivered for a domain in the process of deprication?

Solution 1:

As for depreciation: removing the MX record and blocking port 25 at corresponding A address for the domain is the normal thing to do...