outlook declines to render internal part when Content-Disposition: inline on actual body
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Description

I've been experimenting with different forms of protected headers.

I tried modifying the Multilayer PGP/MIME Message with Protected Headers and Legacy Display Part , which has this structure:

A└┬╴multipart/encrypted
B ├─╴application/pgp-encrypted
C └─╴application/octet-stream
   ↧ (decrypts to)
D  └┬╴multipart/signed
E   ├┬╴multipart/mixed ← Cryptographic Payload
F   │├─╴text/plain ← Legacy Display Part
G   │└─╴text/plain
H   └─╴application/pgp-signature

I'm attaching here two different versions of this structure.

The "normal" variant comes directly from draft -02, following the recommendations there:

Its interior (after decryption) is:

The "inline" variant where the original body (part G above) has an additional header of Content-Disposition: inline:

Its interior (after decryption) is:

(i'm experimenting with this "inline" variant to try see whether it is an improvement for other systems, see the screenshots project).

However, the "inline" variant actually doesn't render part G at all. Here are the two screenshots:

normal:


inline:

I'm not sure what it is about the addition of this inner header which makes Outlook appear to swallow the internal part.

Details

Version
GPGOL 2.4.4
dkg created this task.Feb 4 2020, 12:43 AM
dkg added a comment.Feb 5 2020, 12:46 AM

I've just tested this with GpgOL 2.4.6~beta3 as well, and while the i see the same issue :( (though the legacy display part is not shown, thanks to your fix of T4796).

Here's the screenshot with 2.4.6~beta3:

aheinecke triaged this task as Normal priority.
aheinecke added a subscriber: aheinecke.

I remember that I tested inline content-disposition handling in Outlook without GpgOL and try to do the same handling as Outlook would handle them. But then at the very least It should be shown as an attachment and not hidden.