You will have to use the Delegates in Tools / Options.
I am not sure the depth of this question, so I am assuming a user wants to give rights to all outlook folders, including callendar and Contacts. You may just want to get that users password. But deligates are the most elegant and secure. Unfortunately there is no global set.
In the active directory under Exchange options under the user account, you can use the "send on behlaf of" options. This requires admin rights of course to set this up.
From you posts, it looks as if you have some admin duties. If I can recomend a few links for you as resources try this:
MS Technet Office site ( a great in-depth resource) :http://www.microsoft.com/technet/security/...ech/office.mspxMicrosoft Office website
:Ast;y, get the Using Mocrosoft Office 2003 fat book (Microsoft Press). It needs to be next to your desk. It has tons of very useful in-depth technical info, is easy to read and very useful.