Outlook Inbox does not refresh

[brads]

G'day,

I have a question. We have an issue where our outlook
clients do not seem to be refreshing when new mails come
through. the only way to have them display in the inbox
is to click on another folder (like Sent items) and then
click back in the Inbox.

Does anyone have any thoughts on what may be causing
this? does it sound server, network or client related?

Thanks
BS