Outlook Webmail and Exchange 2000

I think this is possible, im just not sure how to go about doing it…

How do i set exchange to allow people to access other people’s outlook webmail/calenders e.t.c without having to supply a username and password (Usually the network details tolog on)

At the moment, User1 can access Manager1’s webmail, but has to supply the Manager1’s username and password, which we dont want. We want it so it dont ask for such details and it lets us into the webmail straight away.

Like i said.. im pritty sure it can be done, im just not sure how.

Thanks!