"More better" approach?

[SM]

At 12:07 27-06-2008, Tuc at T-B-O-H.NET wrote:
>         I'm wondering if there is something that specifies the "preferred"
>way of using IPv6 when it comes to MX records.
>
>         Currently, my personal domains has the following MX:
>
>         0 - personalmachine-v6 (IPv6 address ONLY)
>         10- personalmachine (IPv4 address ONLY)
>         15- MX relay (Which many people now claim isn't required, but IPv4)
>
>         I've caught flack before from mailing lists and others that having
>my 0 level MX as IPv6 only "Just isn't right".  Some online "DNS Reporting"
>services or other start to claim I can't be contacted, etc.

You'll see something like "Could not resolve domain".

>         Is there a "Best Practice" or "In MA's opinion" about this? I'm
>looking to bring up our major mail server with an IPv6 address, and I
>didn't know if continuing to make it the lowest MX is the best idea, or
>just making the record contain a v4+v6 address. I'm not exactly sure what
>my original reasoning was, or if its valid anymore.

RFC 3974 discusses the issue.  If you point the lowest MX to a 
IPv6-only host, your mail will not be accepted by a lot of sites, 
including a large email service provider.  You can get around the 
problem with a host pointing to a v4 and a v6 address.

Regards,
-sm