PST Files

PST (Personal Storage Table) is a proprietary file format that the Microsoft Corporation created in order to store copies of emails, tasks, address books, and calendar events in Microsoft email and messaging programs such as Microsoft Outlook. The data format is provided for free in order to permit other companies to use the data, but it is controlled by Microsoft.

How Does a PST File Work?

Microsoft Outlook stores calendar events and email messages in a PST or an offline storage table (OST) file depending on the specific configuration of the email client. Typically, users store archived items in a PST file, and the OST stores data that is accessed when the computer is offline. The user or the email client (automatically) can add information to PST files. When emails are moved to a PST file for storage on a business or school network, the email is no longer counted against the user if the network administrator has assigned storage limitations on email accounts. Passwords may be assigned to a PST file. However, Microsoft uses weak encryption for this capability and there are a large number of third party tools available which can crack the password protection.

PST File Support

Microsoft Outlook, Windows Messenger, and the Microsoft Exchange Client supports the PST file format. The file format is open and Microsoft provides free access and free patent licensing to the file format specification. When Microsoft first adopted the file format, it was not compatible with other software applications. Since then, the libpst project that is released under the GPL license has been developed. It has tools that can convert PST files into open formats such as LDAP Data Interchange and mbox formats.

What Restrictions Are There for PST Files?

Before Microsoft Outlook's 2003 release, PST files were limited to 2 GB in size before they would become unstable. For power users, this would result in having to create multiple PST files in order to save a significant amount of email. Since Outlook 2003, however, the PST file format was changed from ANSI to Unicode, which has allowed the maximum size of a PST file to be increased to 20 GB.

How Do You Export a PST File?

Step 1 – Open the Outlook program by double clicking the program icon on the computer's desktop.

Step 2 – Select “File” and “Import and Export.”

Step 3 – Select “Export to File," then click “Next.”

Step 4 – Choose “Personal Folder File (.PST)” then click “Next.”

Step 5 – Select the folder to save or export the file using the file chooser, then click “Next.”

Step 6 – Enter a name for the new PST file in the “File Name” box then click “OK” and “Finish.”

How to Import a PST File into Outlook

Step 1 – Copy the PST file to the computer's desktop if it is stored on a CD or DVD. Once copied, right click the file icon and uncheck the “Read Only” check-box if selected.

Step 2- Double-click the program icon on the computer's desktop to open Microsoft Outlook.

Step 3 – Select “File” and “Import and Export.”

Step 4- Choose “Import from another program or file” then click “Next.”

Step 5 – Select “Personal Folder File (.pst)” and click “Next.”

Step 6 – Select the PST file to import using the file chooser then click “Next.”

Step 7 – Click “Finish” after the file import is complete.