diff --git a/mu4e/mu4e-actions.el b/mu4e/mu4e-actions.el
index d7d95ddd..282c3937 100644
--- a/mu4e/mu4e-actions.el
+++ b/mu4e/mu4e-actions.el
@@ -1,4 +1,4 @@
-;;; mu4e-actions.el -- part of mu4e, the mu mail user agent
+;;; mu4e-actions.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2019 Dirk-Jan C. Binnema
 
@@ -36,6 +36,11 @@
 (declare-function mu4e~proc-extract     "mu4e-proc")
 (declare-function mu4e-headers-search   "mu4e-headers")
 
+(defvar mu4e-headers-include-related)
+(defvar mu4e-headers-show-threads)
+(defvar mu4e-view-show-addresses)
+(defvar mu4e-view-date-format)
+
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 (defun mu4e-action-count-lines (msg)
diff --git a/mu4e/mu4e-context.el b/mu4e/mu4e-context.el
index 11aece41..f4c28919 100644
--- a/mu4e/mu4e-context.el
+++ b/mu4e/mu4e-context.el
@@ -1,4 +1,4 @@
-; mu4e-context.el -- part of mu4e, the mu mail user agent
+; mu4e-context.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2015-2016 Dirk-Jan C. Binnema
 
@@ -27,6 +27,10 @@
 (require 'cl-lib)
 (require 'mu4e-utils)
 
+(defvar mu4e-move-to-trash-patterns)
+(defvar smtpmail-smtp-user)
+(defvar mu4e-view-date-format)
+
 (defvar mu4e-contexts nil "The list of `mu4e-context' objects
 describing mu4e's contexts.")
 
diff --git a/mu4e/mu4e-contrib.el b/mu4e/mu4e-contrib.el
index 95132773..03c932e4 100644
--- a/mu4e/mu4e-contrib.el
+++ b/mu4e/mu4e-contrib.el
@@ -1,4 +1,4 @@
-;;; mu4e-contrib.el -- part of mu4e, the mu mail user agent
+;;; mu4e-contrib.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2013-2016 Dirk-Jan C. Binnema
 
@@ -25,12 +25,14 @@
 
 (require 'mu4e)
 
+(defvar bookmark-make-record-function)
+
 (defun mu4e-headers-mark-all-unread-read ()
   "Put a ! \(read) mark on all visible unread messages."
   (interactive)
   (mu4e-headers-mark-for-each-if
    (cons 'read nil)
-   (lambda (msg param)
+   (lambda (msg _param)
      (memq 'unread (mu4e-msg-field msg :flags)))))
 
 (defun mu4e-headers-flag-all-read ()
@@ -46,7 +48,7 @@
   (interactive)
   (mu4e-headers-mark-for-each-if
    (cons 'something nil)
-   (lambda (msg param) t))
+   (lambda (_msg _param) t))
   (mu4e-mark-execute-all))
 
 ;;;
diff --git a/mu4e/mu4e-draft.el b/mu4e/mu4e-draft.el
index 2b221644..400195af 100644
--- a/mu4e/mu4e-draft.el
+++ b/mu4e/mu4e-draft.el
@@ -1,4 +1,4 @@
-;; mu4e-draft.el -- part of mu4e, the mu mail user agent for emacs
+;; mu4e-draft.el -- part of mu4e, the mu mail user agent for emacs -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2019 Dirk-Jan C. Binnema
 
@@ -77,6 +77,8 @@ If nil, only do so when sending the message."
   (format "mu4e %s; emacs %s" mu4e-mu-version emacs-version)
   "The User-Agent string for mu4e, or nil.")
 
+(defvar mu4e-view-date-format)
+
 (defun mu4e~draft-cite-original (msg)
   "Return a cited version of the original message MSG as a plist.
 This function uses `mu4e-compose-cite-function', and as such all
@@ -413,9 +415,6 @@ You can append flags."
 Replying-to-self is special; in that case, the To and Cc fields
 will be the same as in the original."
   (let* ((reply-to-self (mu4e-message-contact-field-matches-me origmsg :from))
-	 (recipnum
-	  (+ (length (mu4e~draft-create-to-lst origmsg))
-	     (length (mu4e~draft-create-cc-lst origmsg t))))
 	 ;; reply-to-self implies reply-all
 	 (reply-all (or reply-to-self
                         (eq mu4e-compose-reply-recipients 'all)
diff --git a/mu4e/mu4e-icalendar.el b/mu4e/mu4e-icalendar.el
index 1720c0aa..8371078b 100644
--- a/mu4e/mu4e-icalendar.el
+++ b/mu4e/mu4e-icalendar.el
@@ -1,4 +1,4 @@
-;;; mu4e-icalendar.el --- reply to iCalendar meeting requests (part of mu4e)  -*- lexical-binding: t; -*-
+;;; mu4e-icalendar.el --- reply to iCalendar meeting requests (part of mu4e)  -*- lexical-binding: t; -*- -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2019- Christophe Troestler
 
diff --git a/mu4e/mu4e-lists.el b/mu4e/mu4e-lists.el
index 2e5c7610..0540f442 100644
--- a/mu4e/mu4e-lists.el
+++ b/mu4e/mu4e-lists.el
@@ -1,4 +1,4 @@
-;;; mu4e-lists.el -- part of mu4e, the mu mail user agent
+;;; mu4e-lists.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2016 Dirk-Jan C. Binnema
 
diff --git a/mu4e/mu4e-mark.el b/mu4e/mu4e-mark.el
index c423500f..4b637bd7 100644
--- a/mu4e/mu4e-mark.el
+++ b/mu4e/mu4e-mark.el
@@ -1,4 +1,4 @@
-;; mu4e-mark.el -- part of mu4e, the mu mail user agent
+;; mu4e-mark.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2019 Dirk-Jan C. Binnema
 
@@ -356,7 +356,7 @@ user which one)."
     (let ((markpair))
       (maphash
 	(lambda (docid val)
-	  (let ((mark (car val)) (target (cdr val)))
+	  (let ((mark (car val)))
 	    (when (eql mark 'something)
 	      (unless markpair
 		(setq markpair
@@ -421,7 +421,7 @@ If NO-CONFIRMATION is non-nil, don't ask user for confirmation."
     (when (or (null mu4e~mark-map) (zerop (hash-table-count mu4e~mark-map)))
       (mu4e-warn "Nothing is marked"))
     (maphash
-      (lambda (docid val)
+      (lambda (docid _val)
 	(save-excursion
 	  (when (mu4e~headers-goto-docid docid)
 	    (mu4e-mark-set 'unmark))))
diff --git a/mu4e/mu4e-message.el b/mu4e/mu4e-message.el
index e2421fb4..3d4ea2bf 100644
--- a/mu4e/mu4e-message.el
+++ b/mu4e/mu4e-message.el
@@ -1,4 +1,4 @@
-;;; mu4e-message.el -- part of mu4e, the mu mail user agent
+;;; mu4e-message.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2012-2018 Dirk-Jan C. Binnema
 
@@ -30,6 +30,9 @@
 (require 'mu4e-utils)
 (require 'flow-fill)
 
+(defvar mu4e~view-message)
+(defvar shr-inhibit-images)
+
 (defcustom mu4e-html2text-command
   (if (fboundp 'shr-insert-document)
     'mu4e-shr2text
@@ -231,7 +234,7 @@ unless PREFER-HTML is non-nil."
       (setq body (funcall func msg body)))
     body))
 
-(defun mu4e-message-outlook-cleanup (msg body)
+(defun mu4e-message-outlook-cleanup (_msg body)
   "Clean-up MSG's BODY.
 Esp. MS-Outlook-originating message may not advertise the correct
 encoding (e.g. 'iso-8859-1' instead of 'windows-1252'), thus
@@ -331,7 +334,7 @@ Emacs. Based on code by Titus von der Malsburg."
 	 (shr-inhibit-images t))
 	  (shr-render-region (point-min) (point-max)))) msg))
 
-(defun mu4e~html2text-shell (msg cmd)
+(defun mu4e~html2text-shell (msg _cmd)
   "Convert html2 text in MSG using a shell function CMD."
   (mu4e~html2text-wrapper
     (lambda ()
diff --git a/mu4e/mu4e-proc.el b/mu4e/mu4e-proc.el
index 7cad7663..506855b9 100644
--- a/mu4e/mu4e-proc.el
+++ b/mu4e/mu4e-proc.el
@@ -1,4 +1,4 @@
-;; mu4e-proc.el -- part of mu4e, the mu mail user agent
+;; mu4e-proc.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2019 Dirk-Jan C. Binnema
 
@@ -92,7 +92,7 @@ removed."
       (car objcons)))))))
 
 
-(defun mu4e~proc-filter (proc str)
+(defun mu4e~proc-filter (_proc str)
   "Filter string STR from PROC.
 This process the the 'mu server' output. It accumulates the
 strings into valid sexps by checking of the ';;eox' `end-of-sexp'
@@ -287,7 +287,7 @@ Start the process if needed."
 ;; error codes are defined in src/mu-util
 ;;(defconst mu4e-xapian-empty 19 "Error code: xapian is empty/non-existent")
 
-(defun mu4e~proc-sentinel (proc msg)
+(defun mu4e~proc-sentinel (proc _msg)
   "Function called when the server process PROC terminates with MSG."
   (let ((status (process-status proc)) (code (process-exit-status proc)))
     (setq mu4e~proc-process nil)
diff --git a/mu4e/mu4e-speedbar.el b/mu4e/mu4e-speedbar.el
index 6f9d4f1e..4849373d 100644
--- a/mu4e/mu4e-speedbar.el
+++ b/mu4e/mu4e-speedbar.el
@@ -1,4 +1,4 @@
-;;; mu4e-speedbar --- Speedbar support for mu4e
+;;; mu4e-speedbar --- Speedbar support for mu4e -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2012-2018 Antono Vasiljev, Dirk-Jan C. Binnema
 ;;
@@ -88,7 +88,7 @@
 		  maildir-name))
 	(mu4e-get-maildirs)))))
 
-(defun mu4e~speedbar-maildir (&optional text token ident)
+(defun mu4e~speedbar-maildir (&optional _text token _ident)
   "Jump to maildir TOKEN. TEXT and INDENT are not used."
   (dframe-with-attached-buffer
     (mu4e-headers-search (concat "\"maildir:" token "\"")
@@ -106,13 +106,13 @@
 	      (mu4e-bookmark-query bookmark)))
     (mu4e-bookmarks)))
 
-(defun mu4e~speedbar-bookmark (&optional text token ident)
+(defun mu4e~speedbar-bookmark (&optional _text token _ident)
   "Run bookmarked query TOKEN. TEXT and INDENT are not used."
   (dframe-with-attached-buffer
     (mu4e-headers-search token current-prefix-arg)))
 
 ;;;###autoload
-(defun mu4e-speedbar-buttons (&optional buffer)
+(defun mu4e-speedbar-buttons (&optional _buffer)
   "Create buttons for any mu4e BUFFER."
   (interactive)
   (erase-buffer)
diff --git a/mu4e/mu4e-vars.el b/mu4e/mu4e-vars.el
index 9702b09f..57ce7c95 100644
--- a/mu4e/mu4e-vars.el
+++ b/mu4e/mu4e-vars.el
@@ -1,4 +1,4 @@
-;;; mu4e-vars.el -- part of mu4e, the mu mail user agent
+;;; mu4e-vars.el -- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2019 Dirk-Jan C. Binnema
 
diff --git a/mu4e/mu4e.el b/mu4e/mu4e.el
index 96abb807..0cc747e0 100644
--- a/mu4e/mu4e.el
+++ b/mu4e/mu4e.el
@@ -1,4 +1,4 @@
-;;; mu4e.el --- part of mu4e, the mu mail user agent
+;;; mu4e.el --- part of mu4e, the mu mail user agent -*- lexical-binding: t -*-
 ;;
 ;; Copyright (C) 2011-2016 Dirk-Jan C. Binnema
 
diff --git a/mu4e/org-mu4e.el b/mu4e/org-mu4e.el
index 4f3a5726..55cc4ff5 100644
--- a/mu4e/org-mu4e.el
+++ b/mu4e/org-mu4e.el
@@ -1,4 +1,4 @@
-;;; org-mu4e -- Support for links to mu4e messages/queries from within
+;;; org-mu4e -- Support for links to mu4e messages/queries from within -*- lexical-binding: t -*-
 ;;; org-mode, and for writing message in org-mode, sending them as
 ;;; rich-text
 ;;
@@ -39,6 +39,10 @@
 (declare-function mu4e-message                      "mu4e-message")
 (declare-function mu4e-compose-mode                 "mu4e-compose")
 
+(defvar org-export-skip-text-before-1st-heading)
+(defvar org-export-htmlize-output-type)
+(defvar org-export-preserve-breaks)
+(defvar org-export-with-LaTeX-fragments)
 
 (defgroup org-mu4e nil
   "Settings for the org-mode related functionality in mu4e."
diff --git a/mu4e/org-old-mu4e.el b/mu4e/org-old-mu4e.el
index 0d8151fd..f5fd6677 100644
--- a/mu4e/org-old-mu4e.el
+++ b/mu4e/org-old-mu4e.el
@@ -1,4 +1,4 @@
-;;; org-mu4e -- Support for links to mu4e messages/queries from within org-mode,
+;;; org-mu4e -- Support for links to mu4e messages/queries from within org-mode, -*- lexical-binding: t -*-
 ;;; and for writing message in org-mode, sending them as rich-text
 ;;
 ;; Copyright (C) 2012-2016 Dirk-Jan C. Binnema
@@ -34,6 +34,11 @@
 (require 'org nil 'noerror)
 (require 'org-exp nil 'noerror)
 
+(defvar org-export-skip-text-before-1st-heading)
+(defvar org-export-htmlize-output-type)
+(defvar org-export-preserve-breaks)
+(defvar org-export-with-LaTeX-fragments)
+
 (require 'mu4e)
 
 (defgroup org-mu4e nil