From http://kb.iu.edu/data/aisw.html we read:
In Outlook for Windows, if you have an Exchange mailbox, you can allow others within your Exchange organization to access folders in your Exchange mailbox, including your calendar. You can use Microsoft Outlook to share your mailbox folders and to access others' mailbox folders that have been shared with you.
Outlook allows two types of sharing:
* Folder permissions: This type of sharing allows selected others to view the contents of a specified folder, but does not allow others to send email on your behalf. When setting up folder permissions, you can determine exactly how much access a given person has to your folder, choosing from nine roles with different permissions:
o Owner: Allows full rights to the mailbox, including assigning permissions; you should not assign this role to anyone
o Publishing Editor: Can create, read, edit, and delete all items, and create subfolders
o Editor: Can create, read, edit, and delete all items
o Publishing Author: Can create and read items, create subfolders, and edit and delete items they've created
o Author: Can create and read items, and edit and delete items they've created
o Nonediting Author: Can create and read items, and delete items they've created
o Reviewer: Can read items
o Contributor: Can create items
o None: Gives no permissions for the selected accounts on the specified folder
* Delegates: You can also designate delegates, who can have different permissions but also the additional ability to send email on your behalf. By default, a delegate has Editor permissions on the Calendar and Tasks folders.
Setting folder permissions in Outlook
First, you need to give the other person access permission to both the mailbox and the specific folder in the mailbox. Assign permissions along the entire path down to the folder you want to share; for example, if you want others to have access to a subfolder in your Inbox, you need to assign permissions to the mailbox folder, the Inbox folder, and the subfolder. To set permissions on folders:
1. Open Outlook, and find the Folder List. If you don't see the Folder List, from the Go (Outlook 2007 and Outlook 2003) or View (Outlook 2002 and earlier) menu, click Folder List. Then, from the Folder List, right-click the folder you wish to share (this could be your mailbox, Inbox, or calendar, or a subfolder).
2. From the menu that appears, select Properties, and then click the Permissions tab.
Note: If you do not see the Permissions tab, you probably have Personal Folders set as your default delivery location. In order to grant permissions, set the default delivery location to your Microsoft Exchange mailbox. See In Microsoft Outlook, why is my Exchange email disappearing from my Inbox at work after I read it at home?
3. Click Add... , and select the people to whom you wish to grant permissions. After each selection, click Add-> . When you are done, click OK.
4. You can now select which permissions to grant. If you wish to grant only the ability to view items in this folder, assign the role of Reviewer. For more on permissions, see the list above.
To grant permissions, select a name from the box beneath "Name:" and "Permissions:", and then from the drop-down menu beside "Permission Level:" or "Role:", make your selection. You can also create custom permissions by making selections from the checkboxes and radio buttons within the "Permissions" area. Once you've finished making your selections, click Apply, and then OK.
Important: In the list under "Name:", the group called "Default" includes everyone at Indiana University who has an Exchange account. Under normal circumstances, you should not assign permissions to it; leave it set to None. If you grant any permissions or assign a role to it, you are granting those permissions to everyone with an IU Exchange account.
5. Those to whom you have granted permissions now need to set up Outlook to view your folders.