in_reply_to = notmuch_message_file_get_header (message_file, "in-reply-to");
parse_references (message, parents, in_reply_to);
_notmuch_message_add_term (message, "replyto",
in_reply_to = notmuch_message_file_get_header (message_file, "in-reply-to");
parse_references (message, parents, in_reply_to);
_notmuch_message_add_term (message, "replyto",