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IPv6 incentive? RE: Last Call: draft-klensin-rfc2821bis

2008-03-26 14:44:18
It is pretty clear here that we are talking about a configuration that is 
actually specfically prohibited by 2821.
If you are doing SMTP and claiming to be 2821 compliant you must lookup the MX 
and you must not look at the A if there is no MX there. Any sender that is 
breaking those rules is not compliant with the spec.
Spam is relevant in this regard to the extent that when you have a protocol 
that is under such a level of sustained attack, it is entirely justified for 
receivers to employ strict compliance with the standard as an acceptance 
criteria. If you are not 2821 compliant then no soup for you.
I see no reason at all to extend support for non-compliant systems to the IPv6 
world. On the contrary, it seems to me that this transition is exactly the 
point at which you would want to say that the host name fallback support is 
The argument would become even stronger if it turned out that email comming 
over IPv6 transports could be more easily distinguished from spam than over 
other transports. This might even be turned into an incentive for making the 
IPv6 transition.
What I am thinking here is that we stand a better chance of authenticating IPv6 
address block allocations and thus eliminating bogons. Residential support for 
IPv6 is non-existent today. We have a good chance of getting some BCP type 
agreements out of the likes of MAAWG that could limit botnet and spambot 
potential there.
Lets make IPv6 as clean as possible, leave host name A record fallback to the 
legacy world.

From: ietf-bounces(_at_)ietf(_dot_)org on behalf of Ned Freed
Sent: Wed 26/03/2008 2:48 AM
To: Keith Moore
Cc: John C Klensin; Frank Ellermann; Ned Freed; ietf(_at_)ietf(_dot_)org; Bill 
Subject: Re: Last Call: draft-klensin-rfc2821bis

It might be the case that it's useful for an MTA to have an option to
skip MX lookup for specific destinations because of DNS brokenness at
those destinations.  But this seems to me to be outside of the scope of
the standard.

By the same token, discussions of gatewaying to non-Internet systems could be
considered "outside the standard". But RFC 2821 devotes many pages to
discussing this sort of thing.

Skipping MX lookup is not acceptable as a general
practice, nor is it something we want to encourage.

I never implied that it was acceptable. In fact I'm fairly sure I said
the exact opposite.

In general, it's always been acceptable to configure an MTA to handle
mail in some special-case way for specific domains where there was
specific knowledge such that the special-case handling made sense for
those domains.  The MX-then-A lookup is what you should do in the
absence of any such knowledge.


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