extern uschar *uucp_from_sender; /* For building the sender */
extern uschar *warn_message_file; /* Template for warning messages */
-extern uschar *warnmsg_delay; /* String form of delay time */
-extern uschar *warnmsg_recipients; /* Recipients of warning message */
+extern const uschar *warnmsg_delay; /* String form of delay time */
+extern const uschar *warnmsg_recipients; /* Recipients of warning message */
extern BOOL write_rejectlog; /* Control of reject logging */
extern uschar *verify_mode; /* Running a router in verify mode */