+(defvar eudc-known-protocols '(bbdb ldap))
+
+(defcustom eudc-server-hotlist nil
+ "Directory servers to query.
+This is an alist of the form (SERVER . PROTOCOL). SERVER is the
+host name or URI of the server, PROTOCOL is a symbol representing
+the EUDC backend with which to access the server.
+
+The BBDB backend ignores SERVER; `localhost' can be used as a
+placeholder string."
+ :tag "Directory Servers to Query"
+ :type `(repeat (cons :tag "Directory Server"
+ (string :tag "Server Host Name or URI")
+ (choice :tag "Protocol"
+ :menu-tag "Protocol"
+ ,@(mapcar (lambda (s)
+ (list 'const
+ ':tag (symbol-name s) s))
+ eudc-known-protocols)
+ (const :tag "None" nil))))
+ :version "25.1")