[Fwd: Re: Preferred method of advertizing a dual-stack mx server]

[Dave Wilson]

This is starting to sound like a problem with the remote site's DNS. Any
idea what happens when they try to do an A lookup for mail.example.com?

 > example.net.        IN  MX  10  mail.ipv6.example.com.
 > example.net         IN  MX  20  mail.ipv4.example.com.
 >
 > This will simply try to deliver mail to the ipv6-capable host first,
 > then fall back on the ipv4 host.

Since the vast majority of hosts are working ipv4 hosts, would it be
safe to try

example.net.         IN  MX  10  mail.example.com.
example.net.         IN  MX  20  mail.ipv4.example.com.

--although since we're talking about a broken site here, there's no
guarantee that *any* of the above will work. The site is failing in
unpredictable ways on zones with AAAA records. And if this works for one
site, it might break another 8-)

BTW, if you'd like to test IPv6 SMTP transport, send a mail to
LISTSERV@LISTSERV.HEANET.IE with just the word "thanks" in the body.

Dave