Outlook 2007 Send Mail Problem

[IFATCA]

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.