Re: [ipv6-wg] Real-world IPv6 SMTP experience

[Florian Weimer <]

* Gert Doering:

> Hi,
>
> On Wed, Dec 21, 2005 at 02:42:24PM +0100, Florian Weimer wrote:
>> > If there is an implementation/setup that doesn't
>> > work with the above setup then contact them to let them fix it.
>> 
>> Too many machines to fix, I'm afraid.  The AAAA-masks-A bug manifests
>> itself even if there is no working IPv6 connectivity.  It has been
>> gradually introduced to the general mail server population since
>> mid-2004, and since June 2005, there should be a measurable number of
>> hosts affected by it.
>
> Interesting.
>
> My home DNS setup (since over a year now) looks like this:
>
> greenie.muc.de.		14m32s IN MX	5 kirk.greenie.muc.de.
> kirk.greenie.muc.de.	9m16s IN AAAA	2001:608:4::3
> kirk.greenie.muc.de.	9m18s IN A	193.149.48.167

Selective quoting. 8-) There are a couple more MX records:

greenie.muc.de.         900     IN      MX      15000 mx1.muc.de.
greenie.muc.de.         900     IN      MX      16000 mx-150.space.net.
greenie.muc.de.         900     IN      MX      16500 mx-200.space.net.

These are IPv4-only, and they help to pamper over the AAAA-masks-A
issue.  If a broken Exim installation sees just this record for
kirk.greenie.muc.de:

kirk.greenie.muc.de.	9m16s IN AAAA	2001:608:4::3

it still falls back to the other MXes.

But your experience indicates that this setup should be fairly safe
(especially if you exchange mail regularly with some other site in
Stuttgart which is thought to suffer from the AAAA-masks-A bug 8-).