extern uschar *dns_ipv4_lookup; /* For these domains, don't look for AAAA (or A6) */
extern int dns_retrans; /* Retransmission time setting */
extern int dns_retry; /* Number of retries */
+extern int dns_use_edns0; /* Coerce EDNS0 support on/off in resolver. */
extern uschar *dnslist_domain; /* DNS (black) list domain */
extern uschar *dnslist_matched; /* DNS (black) list matched key */
extern uschar *dnslist_text; /* DNS (black) list text message */
extern BOOL helo_verified; /* True if HELO verified */
extern BOOL helo_verify_failed; /* True if attempt failed */
extern uschar *helo_verify_hosts; /* Hard check HELO argument for these */
-extern uschar *hex_digits; /* Used in several places */
+extern const uschar *hex_digits; /* Used in several places */
extern uschar *hold_domains; /* Hold up deliveries to these */
extern BOOL host_find_failed_syntax;/* DNS syntax check failure */
extern BOOL host_checking_callout; /* TRUE if real callout wanted */
/* MIME ACL expandables */
#ifdef WITH_CONTENT_SCAN
extern int mime_anomaly_level;
-extern uschar *mime_anomaly_text;
+extern const uschar *mime_anomaly_text;
extern uschar *mime_boundary;
extern uschar *mime_charset;
extern uschar *mime_content_description;