- * If the database contains a message with the given message_id, then
- * a new notmuch_message_t object is returned. The caller should call
- * notmuch_message_destroy when done with the message.
+ * If a message with the given message_id is found then, on successful return
+ * (NOTMUCH_STATUS_SUCCESS) '*message' will be initialized to a message
+ * object. The caller should call notmuch_message_destroy when done with the
+ * message.
+ *
+ * On any failure or when the message is not found, this function initializes
+ * '*message' to NULL. This means, when NOTMUCH_STATUS_SUCCESS is returned, the
+ * caller is supposed to check '*message' for NULL to find out whether the
+ * message with the given message_id was found.
+ *
+ * Return value:
+ *
+ * NOTMUCH_STATUS_SUCCESS: Successful return, check '*message'.
+ *
+ * NOTMUCH_STATUS_NULL_POINTER: The given 'message' argument is NULL