how to mark outbox emails for send

[Jacob]

I have over 2000 emails in an outbox that will not go out.
New emails are sent fine. The emails that go out
successfully are in bold italics for the moment they
reside in the Outbox prior to being sent. The 2000 or so
emails stuck in the same Outbox are all normal font.

Is there a way to mark them all to be sent?

Also, why would these emails have ended up in this state
in the first place, that is sitting in the Outbox but not
marked to send?

Thanks in advance