Dumb question about the "Outbox"

I don't use the PM function much but noticed that the last message I sent is stuck in the "Outbox".

Does it remain there until the recipient opens it then moved to "Sent Items"? Or. Is there something I'm missing?

Yes, Bandung, your assumption is correct.

The PM will show/remain in your "outbox" until it is opened by the recipient, and then moves to your "sent" box.