Re: [Asrg] [ASRG] SMTP pull anyone?

John Levine <> Wed, 26 August 2009 18:06 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 4FCDD3A6CB5 for <>; Wed, 26 Aug 2009 11:06:00 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -18.028
X-Spam-Status: No, score=-18.028 tagged_above=-999 required=5 tests=[AWL=-0.688, BAYES_20=-0.74, HABEAS_ACCREDITED_SOI=-4.3, RCVD_IN_BSP_TRUSTED=-4.3, RCVD_IN_DNSWL_HI=-8]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id y9rqSpAfoCoc for <>; Wed, 26 Aug 2009 11:05:59 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 255C03A6AA6 for <>; Wed, 26 Aug 2009 11:05:59 -0700 (PDT)
Received: (qmail 49772 invoked from network); 26 Aug 2009 18:06:02 -0000
Received: from ( by with QMQP; 26 Aug 2009 18:06:02 -0000
DKIM-Signature: v=1; a=rsa-sha256; c=simple;; h=date:message-id:from:to:subject:in-reply-to:cc:mime-version:content-type:content-transfer-encoding; s=k0908;; bh=BMEIuRuB+nSKmOhTSqb7Mm0MoGdd7ha9GDj408TecYY=; b=nuSEWlMrFTHUOYhvEz7BFj7+MXW4Q31HReio1ngSa5vHmat378U01KWbURma6Gik+2C/3lwepxCwz99ZDvbdQ/JbGX+59sGTnlRbLA2a+pv+C7JyPz2UfGbzmuUViDGAB1UAVCkDWATjVHUeHXZQgfi0nWehL644tNOGtWg18+U=
DKIM-Signature: v=1; a=rsa-sha256; c=simple;; h=date:message-id:from:to:subject:in-reply-to:cc:mime-version:content-type:content-transfer-encoding; s=k0908; bh=BMEIuRuB+nSKmOhTSqb7Mm0MoGdd7ha9GDj408TecYY=; b=KfBo3StTP2MPNHuHSaTMQfHBxwFArlgROLL/RAVrVQu9toYUA4+/yI58tBjMDqS4bMASGudhHjkpoTN+HNR9fQtZ6Y3xZWwKYH70mldZTRBWSVtiBdDz/wbJdTsQN6W6/KR46a5zNXhonjpcWxgVGJ3s6xd3jnhtM2wm+qXa0xM=
Date: 26 Aug 2009 18:06:01 -0000
Message-ID: <>
From: John Levine <>
In-Reply-To: <>
X-Headerized: yes
Mime-Version: 1.0
Content-type: text/plain; charset=iso-8859-1
Content-transfer-encoding: 7bit
Subject: Re: [Asrg] [ASRG] SMTP pull anyone?
X-Mailman-Version: 2.1.9
Precedence: list
Reply-To: Anti-Spam Research Group - IRTF <>
List-Id: Anti-Spam Research Group - IRTF <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 26 Aug 2009 18:06:00 -0000

>Rich, does ipv6 change any of this?

I'm not Rich, but the open question at this point is how effective
DNSBLs will be on IPv6.

A DNSBL that blocks a single IP at a time, like the CBL and XBL, would
be unworkable.  A typical v6 setup allocates a /64 to each host which
allows various sorts of clever self-configuration, but also means the
host can easily use a different IP address for every connection it
ever makes. (At one address per millisecond, it would take 500 million
years to run through a /64.)  DNSBLs can and do list ranges, and an
obvious change would be to make the finest listed granularity be a
/64, but we really have no idea how the vast number of v6 addresses
will be handed out, and whether it will be practical to create
listings that cover all of the available addresses for a particular
host without also listing a lot of its neighbors.

This suggests that whitelisting techniques (most likely based on DKIM)
will become much more important to recognize mail from people you know
are credible.