After I send a message, they seem to stay in the Outbox and never go into the Sentbox, is this normal? Do they stay in the Outbox until they are read by the receiver?

 

Yes something like that.. They stay there for a bit then they will go to your outbox...

 

Yes. They stay in Outbox until the recipient reads them. Then they go to your Sent Box.

I've seen some stay in the outbox for a while though - so if the person you're sending to has a full inbox, it might not go through.