Monitoring one's email account and personal information within the business is a much bigger topic than a how-to, so if you are ever asked to configure a manager's account so that s/he can view a subordinate account, here is how it's done in Exchange 2007:

1. Open the Exchange 2007 Management Console
2. Navigate to Recipient Configuration > Mailbox
3. Select the mailbox to be controlled
4. Click "Manage Full Access Permission" on the "Action" panes (right hand side)
5. Click the "Add" button and select the user account that is to be in control
6. Click the "Manage" button
7. Click the "Finish" button
8. Open a browser to OWA and log in as the account that is in control
9. In Outlook Web Access, there is a drowdown arrow next to your username, click it
10. Type in the name of the account modified in step 3
11. A new OWA window will open with the manager in control!

In the screen cast below, we configure an account to mascarade as the test account.