About data files

If you use Microsoft Exchange Server, typically your e-mail messages, calendar, and other items are delivered to and stored on the server.

You can also work offline or use Cached Exchange Mode. A local copy of your items is kept on your computer in an Offline Folder file (.ost). The .ost file is synchronized with the Exchange server. Offline Folder files allow you to work with your items when a connection to the Exchange server may not be possible or wanted.

Your items can also be moved or archived to a Personal Folders file (.pst). Since a .pst file is kept on your computer, it is not subject to mailbox size limits on the server. Outlook can be configured to deliver new items to a .pst file, but doing so has several disadvantages including not being able to work with your items from other computers or when using Microsoft Outlook Web Access with your Exchange e-mail account.

If you don't use an e-mail account on an Exchange server, your e-mail messages, calendar, and other items are delivered to and stored locally in a Personal Folders file (.pst) called Outlook.pst. Outlook.pst is the default data file name.

In Microsoft Office Outlook 2003, a new Personal Folders file format, called Microsoft Outlook Personal Folders file (.pst) is introduced that offers greater storage capacity for items and folders and supports multilingual Unicode data. A file created in the Microsoft Outlook Personal Folders file (.pst) format is not compatible with earlier versions of Outlook and cannot be opened in a previous version of Outlook.

To create a data file that is compatible with earlier versions of Outlook, use the Microsoft Outlook 97-2002 Personal Folders file (.pst) format. This file format is the same as the format that was available in earlier versions of Outlook. It does not support multilingual Unicode data and offers the same storage capacity for items and folders that was available in earlier versions.

To see where default store and additional data files are kept on different versions of Microsoft Windows, see the "Outlook file locations" topic. Keep these points in mind:

• You can save, copy, and move a data file (other than the file used as your default information store) to another location on your hard disk, to a floppy disk, or to a share on the network. But remember that you must have read/write permissions to open Personal Folders files (.pst) from a network share.
• If you need to access any data file that is stored on a network share or on another computer, close any program that might be using that file. A data file can be accessed by only one user or program at a time.
• The .pst data file does not support read-only media.

• Only data files that you created will appear in the Outlook Data Files dialog box (File menu, Data File Management command). Your default data file, Outlook.pst, does not appear in the list.

• When you create a .pst, you can assign a password to the file. A password improves security and reduces the ability of others to view your data. You can select the Save this password in your password list to avoid being prompted for the password each time you open the file. Use strong passwords that combine upper- and lowercase letters, numbers, and symbols. Weak passwords don't mix these elements. Strong password: Y6dh!et5. Weak password: House27. Use a strong password that you can remember so that you don't have to write it down.

  Note  If your Windows user account is not password-protected or other people have access to your Windows user account, do not use the Save this password in your password list option.

• You can create additional data files if you want to organize Microsoft Outlook items into specific folders. For example, you might want to keep all messages from a specific company in a separate data file. When you create the data file, you can use any name for the file. The default name is Personal Folders(1).pst, Personal Folders(2).pst, and so forth. You can use any name for the folder associated with that data file. The default name for the folder that appears in the Outlook Folder List is Personal Folders.
• You can also use AutoArchive to move items to a an archive file (Archive.pst). Unlike exporting, where the original items are copied to the export file but are not removed from the current folder, archiving copies items to the archive file and then removes them from the current folder. AutoArchive allows you to set up a schedule and archive multiple folders at the same time at set intervals.
• A utility called PST Backup enables you to make an exact copy (in the same file format) of a .pst data file, copy the backup file to your hard disk or to a network share, and specify a time interval at which Outlook will prompt you to back up a file. Use the backup file to restore the current .pst file in the event that it becomes corrupted or deleted. To use the utility, you must download it from the Microsoft Office Online Web site.
• When you remove items from a Personal Folders file, your file size will not decrease unless you compact the file.

• You can use a data file to make information, such as Contacts, available to another computer you use or to people you work with. The easiest way to do this is to export (copy) the information to a .pst file using the Import and Export wizard.