Recently, a post in the Microsoft Outlook newsgroups (http://support.microsoft.com/newsgroups/default.aspx) asked this question: "When I configured Outlook to access my Exchange email from home, all of my email messages disappeared from my Inbox at the office. Why would this happen?" This confused poster encountered a common Outlook problem-–the ability to configure different delivery locations on different machines that access the same Exchange mailbox. In Outlook, you can choose to have the Exchange Server system deliver all your email messages to your mailbox on the Exchange server or to a Personal Folders (.pst) file on the local system. If a user at home suddenly decides to change her delivery location to a .pst file, all the email messages in her Exchange Inbox, for example, move to the .pst file's Inbox folder on her home PC. The messages will actually disappear from her Exchange Inbox and reappear in her .pst Inbox. Thus, if a user calls you in a panic because his Exchange Inbox is suddenly empty, one of the first things to check is whether he's reconfigured his default delivery location to a .pst file. If he has, you'll probably first need to explain to him why that wasn't such a good idea (more about that in a minute). Then you can walk him through the steps for changing the delivery location back to the Exchange mailbox. First, open Outlook on the machine configured to deliver messages to a .pst file. Then, in Outlook 2002, select Email Accounts from the Tools menu and choose View or Change Existing Email Accounts. (In Outlook 2000 or Outlook 98, select Services from the Tools menu, then click the Delivery tab.) Click the arrow next to the "Deliver new email to the following location" drop-down box, and select "Mailbox - ." Click OK. Then copy the messages from the .pst file back to the Exchange mailbox. In general, Outlook users who connect to an Exchange server should leave their default delivery location set to their Exchange mailbox. There are a couple of reasons for this directive. First, Exchange and Outlook offer some features that you can't take advantage of if you change your delivery location to a .pst file. For example, Exchange can provide a mechanism for collaboration between users in an organization. A user can share any folder in his or her Exchange mailbox with other users by right-clicking the desired folder and selecting Properties. The folder's Permissions tab lets you specify who should be able to access the folder and what level of access they need. Storing your Calendar on the server lets others in your organization see when you're available for meetings and when you're out of the office. Microsoft's discontinuation of Outlook 2000's and Outlook 98's NetFolders technology makes sharing the information in a .pst file with other users difficult. Thus, if you're connected to an Exchange server and you need to share data with other users on the server, it's best to set your delivery location to the server. If you move your delivery location to a .pst file, you also lose the ability to use Outlook Web Access (OWA) to view your email over a browser. You can't access data stored in a .pst file over OWA. Second, some add-ins, including server-based antispam products and content-filtering products, require email messages to be delivered directly to your Exchange Inbox. Changing your delivery location to a .pst file can cause these types of products to fail. Many corporations insist that employees not change their default delivery location because doing so can create the security risk of users receiving viruses or executable files that are prohibited on corporate networks.