Outlook 2010 will not send some messages

[Lundrat]

I cannot send to some email addresses, such as my own. Others are random that will not be sent. The outgoing message just sits in the outbox.
When I checked my account settings everything was fine and the test messages went thru immediately. If I try and send to someone using the same ISP as myself they go thru as do some on other ISPs.



All of this was working normally a few hours ago.
I have removed and re-created my email account, closed Outlook, re-booted the PC all to no avail. Ran my original Outlook CD and asked it to repair Office and have now ran out of ideas.

Any help would be appreciated