[openpgp] Re: Fwd: New Version Notification for draft-gall agher-openpgp-media-types-00.txt

On 08/08/2025 18:38, Andrew Gallagher wrote:
> In particular, this draft defines:
> 
> * new media types `application/pgp-secret-keys` and `application/pgp- 
> message`
> * a media type parameter `armor`, with value `true` or `false`, to 
> indicate the use or lack of ASCII armor

I believe we should define `application/pgp-message` (or equivalent) 
sooner rather than later, and update RFC3156 accordingly.

I was attempting today to set up mail delivery via a third-party email 
service, but it kept rejecting my encrypted test mails because PGP/MIME 
encrypted parts use `content-type: application/octet-stream`. However, 
it explicitly allows `content-type: application/pkcs7-mime`, meaning 
that S/MIME encrypted emails will get delivered but PGP/MIME will not.

This is not limited to a single provider; I have checked several. Some 
have allowlists of content-types and some have blocklists, but the 
outcomes are similar.

`application/octet-stream` is a blunt object - it should not be 
surprising that it triggers alarm bells in email service providers. It 
may have been forgivable when RFC3156 was first written, less so to 
continue using it in 2025.

IMO we should deprecate the use of `application/octet-stream` in 
PGP/MIME. From my initial experiments, it seems that Apple Mail with the 
GPGTools plugin does not recognise any content-type other than 
`application/octet-stream` for the encrypted part, but Thunderbird will 
happily decrypt such a message without complaint, and Mutt also appears 
to handle it correctly.

It might therefore be premature to start generating messages with a 
"correct" content-type straight away. Ideally, this would have been 
fixed years ago - but the second best time to start is now. While this 
is not a critical change, it should be relatively straightforward, and 
should remove a source of excess breakage.

Thanks,
A

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