Outlook 2007 sending mail problem?

[Rob Marshall]

I'm using Outlook 2007 with Vista Business and can receive mail OK from my
POP3 server. However when I send mail it "hangs" in my outbox and the only
way that I can send it is to right click on the message and select the
"forward" option. This opens the message again with the original addressee in
the "send to" box. If I then send the message again it appears in the outbox
but this time in italics and subsequently sends normally.

How do I resolve this issue?

Thanks in advance for any help.