Hi Henrik,
to do this, you will have to adapt the the function org-mime-org-buffer-htmlize() to mu4e requirements.
This function is supposed to do exactly what you want.
In the current org-mime version it looks like this:
(defun org-mime-org-buffer-htmlize ()
"Create an email buffer containing the current org-mode file
exported to html and encoded in both html and in org formats as
mime alternatives."
(interactive)
(save-excursion
(funcall org-mime-up-subtree-heading)
(cl-flet ((mp (p) (org-entry-get nil p org-mime-use-property-inheritance)))
(let* ((file (buffer-file-name (current-buffer)))
(subject (or (mp "MAIL_SUBJECT") (nth 4 (org-heading-components))))
(to (mp "MAIL_TO"))
(cc (mp "MAIL_CC"))
(bcc (mp "MAIL_BCC"))
;; Thanks for Matt Price improving handling of cc & bcc headers
(other-headers (cond
((and cc bcc) `((cc . ,cc) (bcc . ,bcc)))
(cc `((cc . ,cc)))
(bcc `((bcc . ,bcc)))
(t nil)))
(opts (if (fboundp 'org-export--get-subtree-options) (org-export--get-subtree-options)))
(body (org-get-entry)))
(org-mime-compose body file to subject other-headers opts)))))
The Properties are then
MAIL_SUBJECT:
MAIL_TO and so forth.
Compare it with my version of the function:
(defun org-mime-org-buffer-htmlize ()
"Create an email buffer containing the current org-mode file
exported to html and encoded in both html and in org formats as
mime alternatives."
(interactive)
(org-mime-send-buffer 'html)
(message-goto-to))
The latter is not working with current-versions of org-mime.
To me it seems that the task is to find a way to use the newer org-mime version and to somehow integrate it with mu4e.
Greets,
Nils