What is a PST File?

A PST (Personal Storage Table) file is a data file used by Microsoft Outlook to store your emails, calendar items, contacts, tasks, notes, and other Outlook items. Unlike OST files, PST files are not tied to an Exchange Server account and can be used with various email account types, including POP3, IMAP, and web-based email accounts.

How PST Files Work

PST files serve as independent data containers for Outlook items. They can be created manually by users for various purposes, such as archiving old emails, backing up important messages, or transferring Outlook data between computers. When you create a PST file, you can add it to your Outlook profile and move or copy items to it from other folders.

PST File Location

By default, PST files are stored in the following locations depending on your Windows version:

  • Windows 10/8/7: C:\Users\[username]\Documents\Outlook Files
  • Windows XP: C:\Documents and Settings\[username]\My Documents\Outlook Files

However, users can choose to save PST files in any location on their computer or external storage devices.

PST File Types and Size Limitations

There are two main types of PST files:

  • ANSI PST: Used in Outlook 97-2002, with a size limit of 2 GB.
  • Unicode PST: Used in Outlook 2003 and later, with a theoretical size limit of 50 GB (though Microsoft recommends keeping it under 20 GB for optimal performance).

As PST files grow larger, they may become more prone to corruption and can cause Outlook to run slower.

Common PST File Uses

PST files are commonly used for:

  • Archiving: Moving older emails to a separate PST file to reduce the size of your primary mailbox.
  • Backup: Creating copies of important emails and other Outlook items.
  • Data Transfer: Moving Outlook data from one computer to another.
  • Organization: Separating emails from different projects or time periods into different PST files.
  • Storage: Storing emails from POP3 accounts that don't keep messages on the server.

Common PST File Issues

PST files can encounter various problems, including:

  • Corruption: PST files can become corrupted due to improper Outlook shutdowns, system crashes, or hardware failures.
  • Size Issues: Oversized PST files can lead to performance problems and increased risk of corruption.
  • Password Protection: Forgotten passwords for password-protected PST files can make them inaccessible.
  • Network Storage Problems: PST files stored on network drives can become corrupted more easily.

Fixing PST File Issues

Here are some common methods to resolve PST file issues:

  1. Use Outlook's Inbox Repair Tool (SCANPST.EXE): This built-in tool can repair minor corruption issues in PST files.
  2. Create a New PST File: If a PST file is severely corrupted, creating a new one and importing salvageable data may be necessary.
  3. Split Large PST Files: Breaking up large PST files into smaller ones can improve performance and reduce corruption risk.
  4. Regular Backups: Maintaining regular backups of PST files can prevent data loss in case of corruption.

Best Practices for PST File Management

To maintain healthy PST files and prevent issues:

  • Keep PST files under 20 GB in size.
  • Store PST files on local drives, not network locations.
  • Close Outlook properly to allow PST files to be saved correctly.
  • Regularly use the Compact feature to optimize PST file size.
  • Create regular backups of important PST files.
  • Use archive settings to automatically manage email storage.

Converting Between OST and PST

While Microsoft Outlook doesn't provide a built-in way to convert OST files to PST format, there are several reasons why you might need to do this:

  • Recovering data from an orphaned OST file after an Exchange account is deleted.
  • Migrating from an Exchange environment to a different email system.
  • Creating a portable backup of your Exchange mailbox data.

Third-party tools are available that can convert OST files to PST format, allowing you to access the data independently of the original Exchange account.