extern auth_instance auth_defaults; /* Default values */
extern uschar *auth_defer_msg; /* Error message for log */
extern uschar *auth_defer_user_msg; /* Error message for user */
-extern uschar *auth_vars[]; /* $authn variables */
+extern const uschar *auth_vars[]; /* $authn variables */
extern int auto_thaw; /* Auto-thaw interval */
#ifdef WITH_CONTENT_SCAN
extern int av_failed; /* TRUE if the AV process failed */
extern int expand_forbid; /* RDO flags for forbidding things */
extern int expand_nlength[]; /* Lengths of numbered strings */
extern int expand_nmax; /* Max numerical value */
-extern uschar *expand_nstring[]; /* Numbered strings */
+extern const uschar *expand_nstring[]; /* Numbered strings */
extern BOOL extract_addresses_remove_arguments; /* Controls -t behaviour */
extern uschar *extra_local_interfaces; /* Local, non-listen interfaces */
#ifndef DISABLE_PIPE_CONNECT
extern const pcre2_code *regex_EARLY_PIPE; /* For recognizing PIPE_CONNCT */
#endif
-extern const pcre2_code *regex_ismsgid; /* Compiled r.e. for message it */
+extern const pcre2_code *regex_ismsgid; /* Compiled r.e. for message ID */
extern const pcre2_code *regex_smtp_code; /* For recognizing SMTP codes */
-extern uschar *regex_vars[]; /* $regexN variables */
+extern const uschar *regex_vars[]; /* $regexN variables */
#ifdef WHITELIST_D_MACROS
extern const pcre2_code *regex_whitelisted_macro; /* For -D macro values */
#endif