minor improvments

message.py

@@ -22,6 +22,10 @@ async def messenger():
         while not mailbox.outbox.empty():
             message = mailbox.outbox.get()
 
+            # Assert mailbox for target.
+            if message.target not in mailroom.subs:
+                mailroom.create_mailbox(message.target)
+
             # Get mailbox of target and put mail there.
             target_mailbox = mailroom.get_mailbox(message.target)
             print(f"{mailbox.name} -> {target_mailbox.name}: {message.text}")