extern BOOL directory_make(const uschar *, const uschar *, int, BOOL);
#ifndef DISABLE_DKIM
-extern uschar *dkim_exim_query_dns_txt(uschar *);
+extern uschar *dkim_exim_query_dns_txt(const uschar *);
extern void dkim_exim_sign_init(void);
extern BOOL dkim_transport_write_message(transport_ctx *,