outbox vs. sentbox

[Aucilla]

What's the difference between the "outbox" and the "sentbox" in the message section. I have a few items in my outbox that are dated months ago. Does that mean that the people I sent them to never got them? Or read them?

And what do the little flags mean to the left of messages in the outbox?

And why does the porriage bird lay its eggs in the air?

And why is there air?

[Tom Keels]

Outbox = Sent but not read
Sentbox = Sent AND read

Flags out to the side allow you to selectively mark messages for deletion.