Re: [ietf-smtp] DKIM and DMARC, Email explained from first principles
Sam Varshavchik <mrsam@courier-mta.com> Tue, 25 May 2021 10:52 UTC
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From: Sam Varshavchik <mrsam@courier-mta.com>
To: ietf-smtp@ietf.org
Date: Tue, 25 May 2021 06:52:12 -0400
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Subject: Re: [ietf-smtp] DKIM and DMARC, Email explained from first principles
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John Levine writes: > As you say, merely having a DKIM signature tells you nothing, but > after you watch a mail stream for a while, you see that some DKIM > signers send clean mail and some send lousy mail and adjust your > filters appropriately. To me that's not fundamentally different from filtering based on the sending IP address. I do not see both bad and clean mail coming out of the same IP address, differing only in the sending domain. In that situation, and where the signatures are applied by the mail host to their users, then I could see this argument. I should clarify this. I see that occasionally. But when it does, I seem to always end up moving my goalposts, and conclude that the mail provider itself is rogue, and made a business decision to go into the business of providing spam outsourcing services, with some non-spam mail services on the side. So I treat it as a bad mail source. Ss long as mail recipients are willing to tolerate spam-friendly mail service providers, and relying on the domain signature to filter out their spamming customers, this situation will never change. I don't accept the premise that accepts bad and clean mail coming out of the same IP address using "oh well just use a domain signature" as a solution. > Large mail systems all do this. We hoped that > there would be shared DKIM reputation lists like there are shared IP > lists but so far that hasn't happened. This is never going to happen. Domains are relatively cheap. If a domain acquires negative social credit it'll be discarded and replaced by a new one. > The original point of DMARC was for B2C or B2B mail from heavily > phished domains like Paypal, that could say please discard anything > from us that fails DMARC and we understand that might be some real > mail. (All of Paypal's mail just says "something happened, look at our > web site".) It still works pretty well for that. Eh, no. A large majority of user-facing mail clients are now hiding the sending mail address, and showing only the name, up front. From: "Paypal Customer Service" <kjsdfjklk@934iowero.us> Most people will see "Paypal Customer Service". Valid domain signature for 934iowero.us, and straight it goes into your Inbox.
- [ietf-smtp] Email explained from first principles Kaspar Etter
- Re: [ietf-smtp] Email explained from first princi… Bron Gondwana
- Re: [ietf-smtp] Email explained from first princi… Alessandro Vesely
- Re: [ietf-smtp] Email explained from first princi… Viktor Dukhovni
- Re: [ietf-smtp] Email explained from first princi… Viktor Dukhovni
- Re: [ietf-smtp] Email explained from first princi… Kaspar Etter
- Re: [ietf-smtp] Email explained from first princi… Peter J. Holzer
- Re: [ietf-smtp] Email explained from first princi… John Levine
- Re: [ietf-smtp] Email explained from first princi… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… John Levine
- Re: [ietf-smtp] Email explained from first princi… Dave Crocker
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Dave Crocker
- Re: [ietf-smtp] Email explained from first princi… John R Levine
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… John Levine
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Dave Crocker
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Dave Crocker
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Dave Crocker
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Matthias Leisi
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Dave Crocker
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… John Levine
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Sam Varshavchik
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… Nathaniel Borenstein
- Re: [ietf-smtp] DKIM and DMARC, Email explained f… John C Klensin
- Re: [ietf-smtp] Email explained from first princi… Kaspar Etter
- Re: [ietf-smtp] Email explained from first princi… John R Levine
- Re: [ietf-smtp] Email explained from first princi… John R Levine
- Re: [ietf-smtp] Email explained from first princi… Kaspar Etter
- Re: [ietf-smtp] Email explained from first princi… John R Levine
- Re: [ietf-smtp] Email explained from first princi… Richard Clayton
- Re: [ietf-smtp] Email explained from first princi… Alessandro Vesely
- Re: [ietf-smtp] Email explained from first princi… John C Klensin
- Re: [ietf-smtp] the point of domain authentication John R Levine
- Re: [ietf-smtp] mailing lists are complicated, wa… John Levine
- Re: [ietf-smtp] the point of domain authentication Sam Varshavchik
- Re: [ietf-smtp] the point of domain authentication John Levine
- Re: [ietf-smtp] mailing lists are complicated, wa… Alessandro Vesely
- Re: [ietf-smtp] mailing lists are complicated, wa… John R Levine
- Re: [ietf-smtp] mailing lists are complicated, wa… Dave Crocker
- Re: [ietf-smtp] Email explained from first princi… Richard Clayton
- Re: [ietf-smtp] mailing lists are complicated, wa… Alessandro Vesely