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

John Levine <johnl@taugh.com> Fri, 26 November 2021 04:29 UTC

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From: John Levine <johnl@taugh.com>
To: dmarc@ietf.org
Cc: weihaw@google.com
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Subject: Re: [dmarc-ietf] Reversing modifications from mailing lists
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It appears that Wei Chuang  <weihaw@google.com> said:
>If the RFC2045 canonical representation at the final destination can be the
>same as the canonical representation at the original sender, ...

When we were working on DKIM canonicalization we had lengthy discussions about
what to do about MIME and we decided not to even try.  There is no canonical
representation of a MIME message and nobody to my knowledge has ever tried to
describe what it would mean for two MIME messages to be equivalent, since they
could vary in a fantastic number of ways.  Part separators can change, the
pieces of multipart/whatever might change, line breaks in quoted-printable
and base64 can change, spacing and capitalization of headers can change, and
that's just what I can think of in two minutes.

R's,
John

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