current usage of AAAA implicit MX?

[SM]

Hello,

I'm copying a message from Tony Hansen who is the shepherd for RFC 2821bis.

At 13:32 03-04-2008, Tony Hansen wrote:

Before we can put the issue of AAAA implicit MX to bed, we need to 
get an answer to the question of how much AAAA implicit MX is already 
being used in the real world.

It's been postulated that the current deployment of this and its use 
is low. However, RFC 3974 (SMTP Operational Experience in Mixed 
IPv4/v6 Environments), was published three years ago, and it mandates 
AAAA implicit MX (as much as an informational document can mandate anything).

So I'm looking for information from people who are currently working 
in the IPv6-based email world.

I'm assuming that a number of email sites over in Asia are already 
IPv6-enabled, and there are probably other enclaves as well. So I'm 
looking for information on actual email deployment and sites.

I'm looking for help answering these questions:

   *	How are existing IPv6-enabled mail sites actually dealing with
	missing MX records?

   *	Are the IPv6-enabled email sites mostly following the
	recommendations found in RFC 3974?

   *	How widespread is the use of implicit MX with AAAA records? That
	is, how prevalent are email sites that do not have MX records
	but do have AAAA records?

   *	How big is the existing IPv6-enabled email world?

   *	What problems, if any, has been experienced by following RFC
	3974?

Also, who else could I send this message to in order to gain 
additional insights?

Thank you!

     Tony Hansen
     "shepherd for 2821bis"
     tony at att.com