(DMARC) Why mailing lists are only sort of special

"John R Levine" <johnl@taugh.com> Wed, 16 April 2014 02:18 UTC

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Date: 15 Apr 2014 22:18:26 -0400
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From: "John R Levine" <johnl@taugh.com>
To: "ietf@ietf.org" <ietf@ietf.org>
Subject: (DMARC) Why mailing lists are only sort of special
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Murray asked a couple of interesting questions, which I will address 
separately in separate message threads.

To the question why are mailing lists special, they're somewhat special, 
but they're more interesting here as canaries in the coal mine.

As a rough estimate, roughly 90% of e-mail is spam, most of what's left is 
bulk broadcast mail, most of what's left after that is transactional 
sort-of-broadcast mail, and the little bit at the end is discussion lists, 
individual mail, and some miscellaneous other stuff.  Nonetheless, people 
have consistently said that they want to get their individual mail, and 
don't care about the broadcast mail.  I'm not aware of surveys where they 
ask specifically about discussion lists, but since each message is 
generally hand written by an identifiable person, I'd expect people to 
consider it a lot closer to individual mail than the daily blast from 

So mailing list mail is special for the same reason individual mail is 
special--it's the mail people want.

The reason it's not special is that it's just the most visible example of 
a wide variety of legitimate useful mail that DMARC can't describe, and 
that are broken by DMARC policies other than p=none.

For example, I send and receive my Yahoo mail on my Gmail account, and 
have done so for years.  Gmail makes the obvious checks to ensure that 
it's my account, so it's just as secure as sending from Yahoo, and it's 
useful.  Or it was useful until last weekend. Now a lot of it bounces.

Or there's the WSJ's mail an article feature.  It's useful, nobody abuses 
it.  Yahoo users can't use it any more.

There's lots of these, and the only thing "wrong" with them is that DMARC 
can't distinguish them from other somewhat similar mail sources that send 
spam.  The proposals I'm seeing from the DMARC cartel are basically Google 
Purge applied to e-mail:


Surely we can do better than that, but that's the next message.

John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail.