This is normally related to UDP. Read here or have your Network Admin check
it out:
http://support.microsoft.com/kb/839226/en-us
"Ross_Arnold" wrote:
> Hi,
>
> I have installed Outlook 2000 on a Windows XP machine and is connected to an
> Exchange 2003 mail server. I have only had this problem since upgrading to XP.
> When a new mail is sent it is not appearing in the Inbox until you click on
> a different folder i.e. deleted items and then click back the Inbox.
>
> Could anybody please help as this is driving me mad!
>
> Thanks
>
> Ross