At 09:40 +0200 on 04/07/2008, Michael Storz wrote about deprecate
implicit MX even for IPv4:
The longer I follow this discussion and think about it, I am feeling that
the cleanest solution would be to deprecate implicit MX even for IPv4. In
the meantime I am convinced the implizit MX is a defect of RFC 2821. It
was introduced more than 20 years ago as a workaround to get the routing
via explizit MX RRs running.
While I agree with you that the time has come to depreciate implicate
MX for IPv4, I do not think addressing this issue/need should be
commingled with a ban on implicate MX for IPv6. IOW: Ban the
Implicate IPv6 MX as one effort and ban the Implicate IPv4 MX as a
separate effort or a failure of the IPv4 ban may prevent the IPv6 ban
from being effective. I see the 2 bans as SEPARATE issues and thus
should be addresses separately or we will have the IPv4 issue affect
the IPv6 issue. I see the IPv6 issue as something that needs to be
addressed NOW while the IPv4 issue can be fought another day if
needed. We have lived with this problem for 20 years and can live
with it, if needed, for a few more years. The IPv6 issue can NOT be
ignored or we will just end up in the same situation with AAAA record
usage as we have with A record usage. The time to act on AAAA usage
is NOW while the A usage can be addressed later/eventually.