A long time ago I deleted one contact from my list but didn't block him. Today he started a chat with me and we talked. Then after some time, when I sent a message to him, messenger said that my message couldn't be delivered to recipient. I understood that he went offline and because he is not in my list, offline messaging system didn't work and my message couldn't be delivered. So I added him back to resend my last message as an offline message. It was sent successfully, at least I didn't get any warning from messenger.

And my question: if I delete him again now, is my offline message deleted from servers or does he still receive that message when he signes in even he isn't in my list at that moment?