BOOL helo_verified = FALSE;
BOOL helo_verify_failed = FALSE;
uschar *helo_verify_hosts = NULL;
-uschar *hex_digits = US"0123456789abcdef";
+const uschar *hex_digits = CUS"0123456789abcdef";
uschar *hold_domains = NULL;
BOOL host_checking = FALSE;
BOOL host_checking_callout = FALSE;
/* MIME ACL expandables */
#ifdef WITH_CONTENT_SCAN
int mime_anomaly_level = 0;
-uschar *mime_anomaly_text = NULL;
+const uschar *mime_anomaly_text = NULL;
uschar *mime_boundary = NULL;
uschar *mime_charset = NULL;
uschar *mime_content_description = NULL;