+For an open message, all of these headers will be made visible
+according to `notmuch-message-headers-visible' or can be toggled
+with `notmuch-show-toggle-headers'. For a closed message, only
+the first header in the list will be visible."
+ :group 'notmuch
+ :type '(repeat string))
+
+(defcustom notmuch-message-headers-visible t
+ "Should the headers be visible by default?
+
+If this value is non-nil, then all of the headers defined in
+`notmuch-message-headers' will be visible by default in the display
+of each message. Otherwise, these headers will be hidden and
+`notmuch-show-toggle-headers' can be used to make the visible for
+any given message."