Re: IPv6 mail, was Let's try to be productive...

>Agreed that IPv6 DNSBL isn't straightforward, but it may not be necessary.
>
>There is some logic to not accepting mail on IPv6 at all. ...

For a while, sure.  Mail will be the last thing to move to IPv6 because it
is unusual both in that it works flawlessly through extra relays, and you
can pump vast amounts of mail through very small amounts of address space.

On the other hand ...

I expect it will matter a lot who you correspond with.  In China in
particular, they use IPv6 more than we do because they were late to
the IPv4 party.  In a few years we'll likely be seeing mail systems
that mostly work on v6, with only a cruddy gateway to and from v4.  If
you know what EAI is, the mail extension that allows full non-ASCII
addresses, I can easily believe that the mail system will do EAI but
the gateway won't, which will lock you out from all of the users who
don't have legacy ASCII addresses.  (In China, that will be a lot of
people.)

The large v6 address space also makes it possible to do stuff like
assign known bulk senders specific IPs to send to, either by telling
them (ESPs will do anything you tell them to if they think it will
improve their deliverability by 0.1%), or by DNS tricks.  This will
make it easier to notice funkiness like mail from a sender showing up
from places it's not supposed to come from.

I'm in the process of upgrading my v6 mail software to handle address
rules like v4 rules, mostly so I can send mail from networks who never
send mail worth reading directly to the spam trap.  Will advise.

R's,
John
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