+(defcustom mm-enable-external t
+ "Indicate whether external MIME handlers should be used.
+
+If t, all defined external MIME handlers are used. If nil, files are saved by
+`mailcap-save-binary-file'. If it is the symbol `ask', you are prompted
+before the external MIME handler is invoked."
+ :version "21.4"
+ :type '(choice (const :tag "Always" t)
+ (const :tag "Never" nil)
+ (const :tag "Ask" ask))
+ :group 'mime-display)
+