--On Friday, 21 March, 2008 09:03 +1100 Mark Andrews
I think Doug is saying don't let domains with just AAAA
records be treated as valid RHS of email. Today we
have to add records to domains with A records to say that
these are not valid RHS of email. With MX synthesis
from AAAA you create the same problem for domains with
user@<A record owner>
user@<MX record owner>
user@<AAAA record owner> * don't allow this.
With the understanding that this is just my personal opinion (as
editor, I'll do whatever I'm told) _and_ that I'm personally
sympathetic to phasing out even the A record implicit MX...
It seems to be that 2821bis is the wrong place to try to fix
this, especially via a comment posted well after the _second_
Last Call closed. The current phrasing is not an oversight.
It was explicitly discussed on the mailing list and this is the
behavior that people decided they wanted.
My recommendation is that someone generate a new I-D that
suggests that, even though the standard requires support for
both types of implicit MXs, it is not a desirable practice and
that systems supporting mail servers should use explicit MX
records, ordered however they think appropriate to get the
behavior they want. If consensus could be achieved and the
justification were clear enough, such a BCP would probably get
much more attention than a change of a few lines in 2821bis.
Again, just my opinion.
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