On Sun, 6 Apr 2008, Robert A. Rosenberg wrote:

>
> At 11:38 +0200 on 04/05/2008, Michael Storz wrote about Re: current
> usage of AAAA implicit MX?:
>
> >  > - Number of your IPv6 MTAs which must be located via AAAA (ie: Which
> >>  belong to a FQDN with no IPv6 MX).
> >
> >None. And this is also true for IPv4. All of the hundreds of local MTAs in
> >the Munich Scientific Network (MWN) are routed via MX RRs to our MTAs or
> >to the MTAs of their departemental email servers. Port 25 is blocked from
> >the Internet to the MWN since 10 years.
> >
> >Does this answer your question?
>
> Yes. In your case, there is (as there should be) no reason to support
> AAAA-Fallback in the absence of an MX record (since there are no
> missing MX records).
>
> Since you were talking about domains SENDING to you (and your MTAs
> are dual stack), an interesting question is what is the MX status of
> those who send to you via IPv6 - IOW: How many of the MAIL-FROM FQDNs
> have no MX or A records but only AAAA? I am NOT asking you to provide
> this info but only say that it is a useful metric for the
> AAAA-Fallback issue.
>
>

There where none. As I said in that message:

"160 domains have a path back over IPv6, 155 via MX RRs and 5 via A/AAAA
RRs only:"

The 5 hosts without MX RRs were dual-stack.

Michael Storz

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