Jim Fenton wrote:
(2) Although some SMTP servers will continue to be found through A
records for legacy reasons, there is no longer a good reason for any new
server not to have a published MX record.
Then they won't.
And we don't need to alter algorithms that have been in operation for more than
20 years and working well.
Really, it does not make sense to impose changes based on hopeful thinking
rather than compelling need.
SMTP clients (senders) will,
of course, need to continue to look up A records, but since there is
currently no significant use of AAAA records for email routing, we
should not perpetuate this legacy in IPv6 as it is in IPv4.
Please document the problems caused by this legacy, since serious problems are
what ought to dictate changing an installed service.
The added 'complexity' has worked well enough for 20 years, so it's a bit
difficult to assert it as significant now.
Make AAAA records get the same handling as A and you've made the smallest
possible change to Internet email's transport service. Start messing around
with the role of the address record, and you are altering the service at a more
basic architectural level. Absent compelling need, that's usually a poor idea.
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