10.3 Adding an action in the message view

As another example, suppose we would like to search for messages by the sender of the message at point:

(defun search-for-sender (msg)
  "Search for messages sent by the sender of the message at point."
  (mu4e-headers-search
     (concat "from:" (cdar (mu4e-message-field msg :from)))))

;; define 'x' as the shortcut
(add-to-list 'mu4e-view-actions
   '("xsearch for sender" . search-for-sender) t)

If you wonder why we use cdar, remember that the From:-field is a list of (NAME . EMAIL) cells; thus, cdar gets us the e-mail address of the first in the list. From:-fields rarely contain multiple cells.