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Re: Implicit MX and A RRs

2008-03-26 12:56:26

At 07:46 26-03-2008, Tony Hansen wrote:
As the shepherd/pseudo-chair for 2821bis effort, our plan of action is
going to be as follows:

   *)   the implicit MX issue needs to be resolved.

Quoting the text from rfc2821bis-09, Section 5.1:

  "The lookup first attempts to locate an MX record associated with the
   name.  If a CNAME record is found instead, the resulting name is
   processed as if it were the initial name.  If no MX records are
   found, but an address RR (i.e., either an IPv4 A RR or an IPv6 AAAA
   RR, or their successors) is found, the address RR is treated as if it
   was associated with an implicit MX RR, with a preference of 0,
   pointing to that host."

I suggest a change to use the implicit MX rule for A RRs only as follows:

   The lookup first attempts to locate an MX record associated with the
   name.  If a CNAME record is found instead, the resulting name is
   processed as if it were the initial name.  If no MX records are
   found, but an IPv4 A RR is found, the A RR is treated as if it
   was associated with an implicit MX RR, with a preference of 0,
   pointing to that host.

   An implicit MX RR using the IPv6 AAAA RR, or its successor may be
   required as a fallback for operational reasons.  Designers
   implementing such a mechanism should have it turned off
   in the default configuration.

Regards,
-sm
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