Hi,

I suggest to make the media type used for Org mode files consistent with 
the one used by XDG https://gitlab.freedesktop.org/xdg/shared-mime-info
Currently Emacs has text/x-org, however "x-" prefix is not recommended 
by IANA any more, see https://www.rfc-editor.org/rfc/rfc6648 
"Deprecating the "X-" Prefix and Similar Constructs in Application 
Protocols"

Ideally somebody should file a request to IANA to register the text/org 
media type.
https://www.iana.org/assignments/media-types/media-types.xhtml
However I have no idea concerning a conflict due to the .org file name 
suffix. It was used in the past by early versions of Lotus Organizer. 
https://www.iana.org/assignments/media-types/application/vnd.lotus-organizer

I am unsure if gnus-related code should be committed to some other 
repository at first. I am not a gnus user, so I do not mind if an 
alternative change will be committed.

See also
emacs-orgmode: Org mode MIME type. Sun, 21 Jan 2024 20:56:15 +0700.
https://list.orgmode.org/6d94fff4-4d30-4121-bfd1-f267cb5b637c@gmail.com