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Re: [dmarc-ietf] Reversing modifications from mailing lists

Alessandro Vesely <vesely@tana.it> Fri, 26 November 2021 08:03 UTC

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From: Alessandro Vesely <vesely@tana.it>
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Date: Fri, 26 Nov 2021 09:03:33 +0100
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Subject: Re: [dmarc-ietf] Reversing modifications from mailing lists
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On Thu 25/Nov/2021 09:07:36 +0100 Wei Chuang wrote:
> Thanks for the feedback and answers.


You're welcome


> On Wed, Nov 24, 2021 at 3:01 AM Alessandro Vesely <vesely@tana.it> wrote:
>> On Tue 23/Nov/2021 00:28:01 +0100 Wei Chuang wrote:
>>> [...]
>>>
>>> 6. Subject
>>> * Agreed that some simple heuristic as proposed in the draft is a good 
>>> approach.  Perhaps the original subject suffix length also might work 
>>> here too. >>
>> I don't get this, I'm afraid.  What is the subject suffix length?
> 
> Sorry I wasn't too clear here.  It's largely the same idea as the DKIM body
> length "l=" field above except for reformulated for the Subject header and
> its mailing list mutations.  The original sender would encode a length of
> the original subject say "s.l=<value>".  A receiver would only hash the
> right most "s.l=<value>" length string when validating a Subject hash from
> the original sender.  This assumes that mailing lists may prepend a string
> typically for identification.


Oh, yeah.  However, unless we store sl= as an additional DKIM tag, we'd need an 
extra header field such as Subject-Length.  In that case, Original-Subject is 
much more straightforward.

Original-Subject also covers possible AW: to Re: translations.

Finally, the MLM prefix must be short.  It is not acceptable to have an entire 
phrase followed by hundreds of white space before the original subject.


Best
Ale
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