diff --git a/src/app/definition.h b/src/app/definition.h
index 6fb9550..6de84e8 100644
--- a/src/app/definition.h
+++ b/src/app/definition.h
@@ -48,8 +48,9 @@ typedef enum
   MAILBOX_LETTER = 0,
   MAILBOX_PACKAGE,
   MAILBOX_COLLECTED,
+  MAILBOX_TEST,
   MAILBOX_UNKNOWN,
-} MAILBOX_EVENT_e;
+} __attribute__((__packed__)) MAILBOX_EVENT_e;
 
 //Payload structure
 typedef struct