On 2023-05-26 at 07:05:09 UTC-0400 (Fri, 26 May 2023 13:05:09 +0200)
Paul Menzel via Postfix-users <pmen...@molgen.mpg.de>
is rumored to have said:
Dear Postfix folks,
Apple Mail violates the standard [1],
That's no "standard" that's a Mozilla Inc. bug report.
There is no violation of standards here, there is only an *uncommon*
MIME structure.
resulting in attachments only being shown in the HTML view.
How your MUA presents a particular MIME structure is implementation
dependent.
E.g. my MUA shows me a message with attachments as having attachments,
whether it is rendering HTML or not, no matter which part of a
multipart/alternative message it is presenting. That's a MUA design
choice.
This behaviour is to be expected given the incorrect MIME structure
of the message. It is:
multipart/alternative
text/plain
multipart/mixed
text/html
attachment
So when selecting the plain part, you don't see the attachment
associated with the alternative part.
As Viktor noted, this CAN be a legitimate choice. If the "attachments"
are images that only exist to be displayed inline in rendered HTML,
there's no point in trying to present them in a MNUA that only displays
the text/plain part.
The message structure should be:
multipart/mixed
multipart/alternative
text/plain
text/html
attachment
If we wanted to detect such messages, and add a notification or
extract the attachment, what component would be the right part for
such message alteration? A milter?
A milter would be the best choice. Both MIMEDefang and MailMunge (a
descendant of MIMEDefang) could do this, if you can work with the Perl
MIME::Tools module.
(I am aware, that this will break with end-to-end encryption (GPG or
S/MIME).)
It will also break DKIM. Therefore it would be unsuccessful if you were
to do this with mail that you want to relay or forward elsewhere.
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
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