extern uschar *expand_string(uschar *);
extern void header_add(int, char *, ...);
extern void header_add_at_position(BOOL, uschar *, BOOL, int, char *, ...);
extern uschar *expand_string(uschar *);
extern void header_add(int, char *, ...);
extern void header_add_at_position(BOOL, uschar *, BOOL, int, char *, ...);