Remove attachments from emails

Question

I use Mu4e to do email and my emails are stored locally in a maildir. People often send me emails with large attachments. I'd like to keep the emails but not the attachments because I'm paying for storage and would like to keep cost low. What's the best way to remove attachments from selected emails?

Background: I'm using the development version of Emacs and Ubuntu 16.04.

Answer 1

I found the solution hidden in a closed issue on GitHub (thanks to @mankoff):

(defun my-remove-attachment (msg num) 
  "Remove attachment." 
  (let* ((attach (mu4e~view-get-attach msg num))
         (path (mu4e-msg-field msg :path))
         (filename (and attach (plist-get attach :name)))
         (cmd (format "altermime --input='%s' --remove='%s'"  path filename)))
    (when (and filename
               (yes-or-no-p
                (format "Are you sure you want to remove '%s'?" filename)))
      (shell-command cmd)
      (message cmd))))

(add-to-list 'mu4e-view-attachment-actions
             '("remove-attachment" . my-remove-attachment))

This adds a new "attachment action" in Mu4e. When viewing an email, press A, then r to select the action defined above, then enter the number of the attachment. The action will ask you for confirmation before deleting the attachment. The header listing the attachments is not updates but when you leave the email and reopen it, the attachment is gone.

The code assumes that the tool altermime is installed. To install it in Ubuntu, do sudo apt-get install altermime.

Answer 2

The solution given by @tmalsburg worked for me until I switched to the gnus-based message view, which is now the default.

Below is my attempt to adapt this solution to the new view mode. Note that I do not know lisp and reached that solution by trial and error. It works for me, but you should be careful when copying it.

(defun my-mime-part-filename (num)
  "Filename of MIME part numbered num in gnus-article-mode."
  ;; Check whether the specified part exists.
  (when (> num (length gnus-article-mime-handle-alist))
    (error "No such part"))
  ;; Move point to MIME part
  (when (gnus-article-goto-part num)
    ;; Get handle for MIME part at point
    (let ((handle (get-text-property (point) 'gnus-data)))
      (when handle
        ;; Return file name of handle
        (mm-handle-filename handle)
        ))))
(defun my-delete-attachment (num)
  "Remove email attachment from mu4e using altermime." 
  (let* ((path (mu4e-message-field (mu4e-message-at-point) :path))
         (filename (my-mime-part-filename num))
         (cmd (format "altermime --input='%s' --remove='%s'"  path filename)))
    (when (and filename
               (yes-or-no-p
                (format "Remove '%s'?" filename)))
      (shell-command cmd)
      (mu4e-message cmd)
      )))
(defun my-delete-all-attachments (msg)
  "Remove all email attachments in mu4e using altermime."
  (let* ((path (mu4e-message-field msg :path))
         (subject (mu4e-message-field msg :subject))
         (cmd (format "altermime --input='%s' --removeall"  path)))
    (when (yes-or-no-p
           (format "Remove all attachments from '%s'?" subject))
      (shell-command cmd)
      (mu4e-message cmd)
      )))
(add-to-list 'mu4e-view-mime-part-actions
             '(:name "delete-attachment"
                     :handler my-delete-attachment
                     :receives index))
(add-to-list 'mu4e-headers-actions
             '("Delete-all-attachments" . my-delete-all-attachments))

As I said, I do not know lisp (in any flavour) and so there are probably multiple issues with this code. Any suggestion to improve it is more than welcome. In particular, I feel that the line (filename (my-mime-part-filename num)) in my-delete-attachment could (should?) be (filename (gnus-article-part-wrapper num 'mm-handle-filename)), but that last expression returns nil.