Preferred method of advertizing a dual-stack mx server

[Patrice Fournier]

Hi all,

I currently have my mail server set to accept mail from either an IPv4
address or an IPv6 one (a 2002::/16 address at the moment). and added an
AAAA record to the host that is the MX record. Now, with that change, I've
had a report of at least two users who couldn't mail us (nobody at their
domains could).

As soon as I changed the MX to point a host that only had the A address,
mail started to flow again. 

I know both those place use Lotus Notes internally and the servers that
connect to us are using:
Sendmail AIX4.3/8.9.3/jtpda-5.3.3
Sendmail AIX4.3/8.9.3/8.9.3

I don't know which of Notes or Sendmail AIX is causing this problem but I
was wondering which kind of MX setup you know should work with ALL software
out there?

Now, I have those records:
mail.example.com.      IN A    192.0.2.1
mail.example.com.      IN AAAA 2002:C000:0201::1
mail.ipv4.example.com. IN A    192.0.2.1
mail.ipv6.example.com. IN AAAA 2002:C000:0201::1

If I have this MX setup:
example.net.           IN MX   0 mail.example.com.

it doesn't work, the server never ever try to connect to either ipv6/ipv4
address. (now, I must say that I haven't tested receiving mail on the IPv6
interface other than from the local machine and I can
tracepath6/traceroute6 out of the machine but the sending server MUST try
IPv4 if it can't go through with IPv6, right?)

If I have:
example.net.           IN MX   0 mail.ipv4.example.com.
it works obiously, but now I can't receive mail by IPv6...

Now, would there be a drawback or any other kind of problem by using a
setup such as (and would that be the preferred setup considering that the
first one showed causes problems?):
example.net.           IN MX   0 mail.ipv4.example.com.
example.net.           IN MX   0 mail.ipv6.example.com.

Now, I've got many domains to change, and I'd like to be sure of the
solution before I implement it for all of them...

Thanks,


-- 
Patrice Fournier
pfournier@loups.net