diff --git a/emacs/notmuch-address.el b/emacs/notmuch-address.el
index c6f5f111..10eaab19 100644
--- a/emacs/notmuch-address.el
+++ b/emacs/notmuch-address.el
@@ -118,17 +118,30 @@ to know how address selection is made by default."
   :group 'notmuch-send)
 
 (defun notmuch-address-setup ()
-  (let* ((use-company (and notmuch-address-use-company
-			   (eq notmuch-address-command 'internal)
+  (let* ((setup-company (and notmuch-address-use-company
 			   (require 'company nil t)))
 	 (pair (cons notmuch-address-completion-headers-regexp
 		       #'notmuch-address-expand-name)))
-      (when use-company
+      (when setup-company
 	(notmuch-company-setup))
       (unless (memq pair message-completion-alist)
 	(setq message-completion-alist
 	      (push pair message-completion-alist)))))
 
+(defun notmuch-address-toggle-internal-completion ()
+  "Toggle use of internal completion for current buffer.
+
+This overrides the global setting for address completion and
+toggles the setting in this buffer."
+  (interactive)
+  (if (local-variable-p 'notmuch-address-command)
+      (kill-local-variable 'notmuch-address-command)
+    (setq-local notmuch-address-command 'internal))
+  (if (boundp 'company-idle-delay)
+      (if (local-variable-p 'company-idle-delay)
+	  (kill-local-variable 'company-idle-delay)
+	(setq-local company-idle-delay nil))))
+
 (defun notmuch-address-matching (substring)
   "Returns a list of completion candidates matching SUBSTRING.
 The candidates are taken from `notmuch-address-completions'."
diff --git a/emacs/notmuch-company.el b/emacs/notmuch-company.el
index 610e223d..168315ff 100644
--- a/emacs/notmuch-company.el
+++ b/emacs/notmuch-company.el
@@ -47,7 +47,13 @@
 (defun notmuch-company-setup ()
   (company-mode)
   (make-local-variable 'company-backends)
-  (setq company-backends '(notmuch-company)))
+  (setq company-backends '(notmuch-company))
+  ;; Disable automatic company completion unless an internal
+  ;; completion method is configured. Company completion (using
+  ;; internal completion) can still be accessed via standard company
+  ;; functions, e.g., company-complete.
+  (unless (eq notmuch-address-command 'internal)
+    (setq-local company-idle-delay nil)))
 
 ;;;###autoload
 (defun notmuch-company (command &optional arg &rest _ignore)