Alex van den Bogaerdt <alex(_at_)ergens(_dot_)op(_dot_)het(_dot_)net> writes:
Then: people didn't know MX records and thus didn't use them. Or maybe
they did already know about MX records but did not yet support them.
Some fallback mechanism was necessary to bridge the gap between pre-MX
and post-MX time, or else MX didn't stand a chance.
Now: people do know MX records and do use them, except for a couple
of spammers maybe. There is no need anymore to design a fallback.
I think you should collect some data on this before blithely making such
assertions. All my available anecdotes contradict your assumption so
strongly that I find it very dubious.
For example, here at Stanford, there are a ton of departmental servers
that accept mail for some reason, and almost none of them have MX records.
People only add MX records when they need to direct mail addressed to one
system to a different one instead.
In general, you should count on human laziness. If mail works without
adding an MX record, people aren't going to add one. If nothing breaks
when the MX record is missing, no one will notice it is missing.
Russ Allbery (rra(_at_)stanford(_dot_)edu)