It isn't clear how many implementations do more then translating a hostname
into an address record and using it. It is not clear that intranet or
behind-firewall clients use MX records.
Then they're not following the RFCs, which is perfectly fine so long as
you don't expect them to interoperate directly with the outside world.
That won't change. So could you clarify what you've been objecting to?
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
"I dropped the toothpaste", said Tom, crestfallenly.