That's hard to believe. What do you mean by "outlook box"?
Does that meant the outbox folder in Outlook or the outbox folder in
Windows Mail? If the latter:
If there is an accumulation of messages in the Outbox folder, open
the Outbox folder. Move as many of those messages as you can to
the Drafts folder. If any message can't be moved or deleted, apply this
Microsoft fix:
http://support.microsoft.com/kb/941090
Incidentally, that fix was also included in Vista's SP1, so if you haven't
installed that, you are way overdue.
After you have done that, try sending an email message to yourself.
Do you get an error message when you try to send? If so,
right-click on your error message, copy, then paste it into a reply here.
We can't do much troubleshooting without the complete error message.