[Enigmail] invisible attachments in Mail sent from AppleMail

[vv01f]

We periodically get emails of an organization that loves to use their
Apple products but otherwise is quite nice to be informed about.
Just I will miss their attachments when I view email in text-only mode.
To view them I need to enable at least simplified HTML
 and for obvious
and recently highlighted reasons I refuse to do so by default.

Also I am suspecting this problem best is solved by fixing something at
Apple, but they did not respond within 3 Months and there was no fix either.
So I kindly ask if you can mitigate this in tb :)

I hope to help identifying the problem with the structure ob that mail


```


From: ${sender}
Content-Type: multipart/alternative; boundary="Apple-Mail=_${uuid0}"
Date: ${timestamp0}
Subject: ${subject}
Message-Id: <${uuid2}@${sender-domain}>
Mime-Version: 1.0


--Apple-Mail=_${uuid0}
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
charset=utf-8


${Text-Content0}
--Apple-Mail=_${uuid0}
Content-Type: multipart/mixed;
boundary="Apple-Mail=_${uuid1}"


--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: 7bit
Content-Type: text/html;
charset=us-ascii

${HTML-Content2}
--Apple-Mail=_${uuid1}
Content-Disposition: inline;
filename="${attachment1}.pdf"
Content-Type: application/pdf;
x-unix-mode=0644;
name="${attachment1}.pdf"
Content-Transfer-Encoding: base64

${base64-1}
--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: 7bit
Content-Type: text/html;
charset=us-ascii

${HTML-Content1}
--Apple-Mail=_${uuid1}
Content-Disposition: inline;
filename="${attachment0}.pdf"
Content-Type: application/pdf;
x-unix-mode=0644;
name="${attachment0}.pdf"
Content-Transfer-Encoding: base64

${base64-0}
--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
charset=utf-8

${HTML-Content0}

--Apple-Mail=_${uuid1}--

--Apple-Mail=_${uuid0}--

```

[Robert J. Hansen]

Post by vv01f
I hope to help identifying the problem with the structure ob that mail


I hate to be unhelpful, but it doesn't appear as if this has any connection to Enigmail. You might be better off asking in a Thunderbird forum.

[Juergen BRUCKNER]

I'm sorry not to be helpfull in this topic.

But one question:
Why do they send mails in HTML?

Did you try if this problem appears also if the mails are plaintext?

regards
Juergen

Post by vv01f
We periodically get emails of an organization that loves to use their
Apple products but otherwise is quite nice to be informed about.
Just I will miss their attachments when I view email in text-only mode.
To view them I need to enable at least simplified HTML
 and for obvious
and recently highlighted reasons I refuse to do so by default.
Also I am suspecting this problem best is solved by fixing something at
Apple, but they did not respond within 3 Months and there was no fix either.
So I kindly ask if you can mitigate this in tb :)
I hope to help identifying the problem with the structure ob that mail

```


From: ${sender}
Content-Type: multipart/alternative; boundary="Apple-Mail=_${uuid0}"
Date: ${timestamp0}
Subject: ${subject}
Mime-Version: 1.0
--Apple-Mail=_${uuid0}
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain;
charset=utf-8
${Text-Content0}
--Apple-Mail=_${uuid0}
Content-Type: multipart/mixed;
boundary="Apple-Mail=_${uuid1}"
--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: 7bit
Content-Type: text/html;
charset=us-ascii
${HTML-Content2}
--Apple-Mail=_${uuid1}
Content-Disposition: inline;
filename="${attachment1}.pdf"
Content-Type: application/pdf;
x-unix-mode=0644;
name="${attachment1}.pdf"
Content-Transfer-Encoding: base64
${base64-1}
--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: 7bit
Content-Type: text/html;
charset=us-ascii
${HTML-Content1}
--Apple-Mail=_${uuid1}
Content-Disposition: inline;
filename="${attachment0}.pdf"
Content-Type: application/pdf;
x-unix-mode=0644;
name="${attachment0}.pdf"
Content-Transfer-Encoding: base64
${base64-0}
--Apple-Mail=_${uuid1}
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
charset=utf-8
${HTML-Content0}
--Apple-Mail=_${uuid1}--
--Apple-Mail=_${uuid0}--
```
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[Daniel Kahn Gillmor]

Post by vv01f
We periodically get emails of an organization that loves to use their
Apple products but otherwise is quite nice to be informed about.

a more compact summary of the structure of the message generated by
Apple Mail is here:

A └┬╎multipart/alternative
B ├─╮text/plain
C └┬╎multipart/mixed
D ├─╮text/html
E ├─╮application/pdf inline [${attachment1}.pdf]
F ├─╮text/html
G ├─╮application/pdf inline [${attachment0}.pdf]
H └─╮text/html

The message itself is part A, which contains parts B and C.

I've seen this for years from senders using Apple Mail, for all kinds of
attachments, including both application/pdf and image/jpeg

Post by vv01f
Just I will miss their attachments when I view email in text-only mode.

right, by viewing in text-only mode, you're choosing to view B instead
of C. But the attchments themselves are both subparts of C, so they get
hidden. It's possible that if they weren't marked as
Content-Disposition: inline that Thunderbird would show them as an
attachment anyway -- i haven't tested.

Post by vv01f
To view them I need to enable at least simplified HTML
 and for obvious
and recently highlighted reasons I refuse to do so by default.

I'd have agreed with other messages in this thread that your question
was off-topic for enigmail, except for this bit. Users of enigmail have
a stronger reason than users of cleartext mail to prefer the plaintext
view.

So this is a tricky situation. One approach could be to expect
thunderbird to extract all the

on the one hand, Apple Mail is clearly generating the message
suboptimally.

its structure should ideally put the pdf files as attachments *outside*
the multipart/alternative view:

J └┬╎multipart/mixed
K ├┬╎multipart/alternative
L │├─╮text/plain
M │└─╮text/html
N ├─╮application/pdf attachment [${attachment1}.pdf]
O └─╮application/pdf attachment [${attachment0}.pdf]

That way, choosing a preference between text/plain and text/html results
in selection of L or M, leaving the attachments N and O visible for both
situations.

I don't know whether Apple is willing to consider changing how Mail.app
generates MIME structure, or where that would be reported most clearly.
If someone does report it to them, please reply back here with a pointer
to the bug report (or at least a description of the most effective place
to report such a bug).

Another potential optimization/heuristic would be to ask Thunderbird to
pick out specific kinds of MIME subparts even within a
multipart/alternative variant, and to render them as distinct,
downloadable attachments, regardless of any explicit Content-Disposition
header. I'm note conivnced that this is a good idea, but you could
probably document such a recommendation for Thunderbird most effectively
here:

https://bugzilla.mozilla.org/enter_bug.cgi#h=dupes%7CThunderbird

Regards,

--dkg