On Thursday,  1 Mar 2018 at 19:04, Joseph Vidal-Rosset wrote:

[...]

> autoinsert works well  for new org files,  it is a first  good point for
> me. I receive this message: Perform org-mode auto-insertion? (y or n)
> and after replying "y" I get my org file with the bibliography link.
>
> Unfortunately, it does not work in Gnus with the command M-x org-mode on
> a reply to a message, and I do not understand why.

Because switching to org mode is not creating a new file but simply
changing the mode of an existing buffer.  Autoinsert is only for new
files.  What you could do is customise gnus to create your email buffer
with the right content instead.

If there is a predictable circumstance when you want to effect this
auto-insertion in emails, I would suggest you look at gnus posting
styles (section 5.6 of the gnus info manual).  You can specify a default
"body" for an email when created (along with other things, typically a
signature).  For instance, the signature on this email is automatically
inserted by gnus when I respond to an email in the org mailing list.

#+begin_src emacs-lisp
  (setq gnus-posting-styles
        '((".*:lists.org"
           (signature esf/orgmode-signature-version))))
#+end_src 

(much abridged) where lists.org is the group in which org emails are
split to (by gnus) and

#+begin_src emacs-lisp
  (defun esf/orgmode-signature-version ()
    (format "Eric S Fraga via Emacs %s, Org %s\n"
            emacs-version (org-git-version)))
#+end_src 

You could also consider defining entries in *gnus-alias-identity-alist*
which you can then invoke manually on specific emails using
gnus-alias-use-identity, which I have bound to C-c i.  This can insert
default text in the body as well as do other things, much like posting
styles.

gnus is much like org in that if there's something you want to do,
there's more than likely a solution already!  Well, actually, I guess
this is really a feature of emacs...

-- 
Eric S Fraga via Emacs 27.0.50, Org release_9.1.6-191-g90607d