nanog mailing list archives
RE: Incoming SMTP in the year 2017 and absence of DKIM
From: "Keith Medcalf" <kmedcalf () dessus com>
Date: Wed, 29 Nov 2017 13:58:53 -0700
In which case neither will they be RFC compliant. (1) The "inaddr-arpa" ptr from the incoming connection, when resolved, MUST result in a set of IP Addresses which includes the original IP Address. (2) The "name" specified in the HELO/EHLO MUST resolve to an MTA that meets the above reverse/forward resolution requirement. (3) The domain name specified in the envelope-from MUST be resolvable to an MTA that meets the above requirement (1) or be empty. (4) The SPF checking, if done, MUST NOT fail. (5) The connecting MTA MUST NOT speak when not spoken to (that is, it MUST NOT not violate the SMTP chat protocol). If you dump all connections that are do not meet these requirements, you will have eliminated 99% or more of all spam. DKIM signatures do not really add much at all except prove that the message was sent through a server that could calculate a DKIM signature. It says nothing about whether the message is SPAM or not. 99% (or more) of all spam will have violated one or more of rules (1) through (5) long before the message contents are accepted so that the signature can be verified. --- The fact that there's a Highway to Hell but only a Stairway to Heaven says a lot about anticipated traffic volume.
-----Original Message----- From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Eric Kuhnke Sent: Wednesday, 29 November, 2017 11:19 To: nanog () nanog org list Subject: Re: Incoming SMTP in the year 2017 and absence of DKIM Anecdotal experience. I'm subscribed to a lot of mailing lists. Some pass through DKIM correctly. Others re-sign the message with DKIM from their own server.98% of the spam that gets through my filters, which comes from an IPnot in any of the major RBLs, has no DKIM signature for the domain. My theory is that it does introduce somewhat of a barrier to spam senders because they are frequently not in control of the mail server (which may be some ignorant third party's open relay), nor do they have access to the zonefile for the domain the mail server belongs to for the purpose of adding any sort of DKIM record. On Wed, Nov 29, 2017 at 10:12 AM, Michael Thomas <mike () mtcc com> wrote:On 11/29/2017 10:03 AM, valdis.kletnieks () vt edu wrote:On Wed, 29 Nov 2017 09:32:27 -0800, Michael Thomas said: There are quite a few things you can do to get the mailing listtraversal rate > 90%, iirc.Only 90% should be considered horribly broken. Anything thatmakesit difficult to run a simple mailing list with less that at least2 or 39's is unacceptable.I've been saying for years that it should be possible to create the concept of DKIM-friendly mailing lists. In such a case, you could have your nines. Until then, the best you canhope foris the list re-signing the mail and blaming the list owner instead. Mike
Current thread:
- Re: Incoming SMTP in the year 2017 and absence of DKIM, (continued)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM John Levine (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM valdis . kletnieks (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)
- Re: lists and DMARC and ARC, was Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Eric Kuhnke (Dec 01)
- RE: Incoming SMTP in the year 2017 and absence of DKIM Keith Medcalf (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Michael Thomas (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Chuck Anderson (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM John Levine (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)
- Re: Incoming SMTP in the year 2017 and absence of DKIM Grant Taylor via NANOG (Dec 01)