On Fri, 17 Aug 2012, John R. Levine wrote:
Hi. Remember the ASRG? I was hoping it might do a little research.
In talking to people about IPv6 mail, I'm still coming to the conclusion that
anyone who thinks they know how they're going to handle it, beyond the
current toy scale, doesn't understand the problem. Things we might address
include:
I would not expect to accept any IPv6 mail until users come forward to
show me that they wish to correspond with MTAs that have no IPv4
connection ability. While this may happen in the fullness of time, I don't
expect it soon. Now and for the foreseeable future such a system would
have very little connectivity, far less than a blacklisted spam source.
I understand that a non-trivial number of MTAs are currently able to use
IPv6, but I also understand that all of the ones we wish to correspond
with are also capable of using IPv4. Since our anti-spam technology
(Spamhaus) is very dependent on IPv4 blacklists, it would be very
undesirable to add a general IPv6 port. I would add a handful of IPv6 only
sites to a whitelist or subscribe to a responsible whitelist long before
attempting to accept messages from unknown IPv6 mtas.
We are all familiar with the concept that you "can't enumerate badness".
The IPv4 address space is small enough that you actually can, and it
has worked very well for us. In IPv6, I don't think it would work at all.
dan feenberg
NBER
R's,
John
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