extern uschar *message_id_external; /* External form of following */
extern uschar *message_id_domain; /* Expanded to form domain-part of message_id */
extern uschar *message_id_text; /* Expanded to form message_id */
extern uschar *message_id_external; /* External form of following */
extern uschar *message_id_domain; /* Expanded to form domain-part of message_id */
extern uschar *message_id_text; /* Expanded to form message_id */