Subject: [dmarc-ietf] Re: Discussion Thread for Issue 155
From: Tero Kivinen <[email-masked]>
To: "John R Levine" <[email-masked]>
Cc: Alessandro Vesely <[email-masked]>, [email-masked], Murray Kucherawy <[email-masked]>
Date: Sat, 26 Oct 2024 02:34:54 +0300
List-Id: "Domain-based Message Authentication, Reporting, and Compliance (DMARC)" <dmarc.ietf.org>

John R Levine writes:
> > That way a receiver has to manage a list of forwarding recipes for each user.
> 
> Surely it is obvious why this sort of thing does not scale.

Why not?

I have less than half a dozen places that forward emails to me. Then I
have perhaps about few dozen mailing list domains where I have joined.
The list of my forwarding domains has been stable for quite long time
(years), I do not even remember when new indirect mail flow was
created for me from new domains (I have joined new IETF mailing lists,
but they are using same forwarding domain still).

Mail recipient systems already do much more heavy processing for every
single email I receive, doing one list lookup to see which ARC
forwarders to trust is much cheaper than some of those spam filterings
it does.

So why do you think this does not scale?

There will not ever be global trusted ARC signers list, as that list
is different for each user, thus trying to make it global would be
pointless. There is per final mailbox user list but that only will
have few dozen entries. 
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