A PST file (Personal Storage Table) locally stores emails, contacts, calendars, and other in­form­a­tion. It mainly serves as a backup file for POP accounts or for archiving when mailboxes need to be relieved. We explain how PST files work, where they’re stored, and how they differ from OST files.

What is a PST file?

PST stands for Personal Storage Table. A PST file is a personal data container that you can imagine as a com­bin­a­tion of a safe and a file folder. In the PST file, Outlook collects personal, syn­chron­ised user data and saves it as a backup on the computer. PST is a pro­pri­et­ary file format by Microsoft, meaning it is licensed by Microsoft and can generally only be opened with Outlook and a cor­res­pond­ing Outlook account.

The role PST files play for users primarily depends on the type of Outlook account:

  • Outlook with POP accounts (also POP3): You download emails directly from the mail server and save them locally on your computer in the PST format.
  • Outlook with IMAP, Microsoft 365, Exchange, or Outlook.com accounts: ‘Original data’ remain on the mail server, while offline Outlook data files, OST files, are cached on the device. IMAP has used OST by default since Outlook 2013.
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The dif­fer­ences between PST and OST files

Feature PST file OST file
Location Local file on the PC, primarily used with POP accounts Local copy of a server mailbox (Exchange, Microsoft 365, Outlook.com, IMAP)
Syn­chron­isa­tion Changes are im­me­di­ately con­sidered original, no syn­chron­isa­tion with the server Offline changes are synced with the server the next time you’re online
Usage Archiving, backup, storage expansion Offline access to server mailbox
De­pend­ency on account Can be opened in­de­pend­ently of the server Only works with an active account/profile
Risk Loss or damage = original data lost Low risk, as the server acts as the ‘master’

The main advantage of the PST format is its large storage capacity compared to the often limited space of email mailboxes. A PST file lets you manage your Outlook data more flexibly — for example, you can:

What are the benefits of PST files?

The key ad­vant­ages of Outlook and PST files are as follows:

  • Outlook syn­chron­ises various personal or business data and in­teg­rates them into a single interface
  • Creates con­nec­tions between areas that are often separate, such as mailboxes, calendars, and contact lists
  • Allows the archiving of emails, for example, separated into personal and business cat­egor­ies
  • Enables backups of personal Outlook data on your PC
  • Supports the export of data to free up mailbox space or for trans­fer­ring to a new device
Note

In the new Outlook for Windows, PST support is limited: PST files can be opened, searched, and copied, but full editing is not yet possible in all scenarios.

Outlook not only eases the access for users to the data but also allows them to organise their ‘personal storage’, separate PST files into personal and business matters, and dis­tin­guish from linked apps or Outlook al­tern­at­ives.

How to archive PST files auto­mat­ic­ally or manually

Archiving user data is done by moving the data and their folder struc­tures into local PST files. You can decide whether to keep the archived data in your mailbox or auto­mat­ic­ally delete it. Ad­di­tion­ally, you can choose whether to perform the archiving auto­mat­ic­ally at intervals or manually.

  • Automatic archiving

  • File > Options > Advanced > AutoArchive

  • Set intervals (e.g., every x days/weeks/months)

  • Choose storage location and specify when old data should be deleted

  • Manual archiving

  • File > Tools > Clean Up Old Items

  • Choose archiving by age or folder

  • Move data spe­cific­ally into a PST file

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How to find PST files in Outlook

The storage location of a PST file depends on the Outlook version, account type, and settings. Typical default paths are:

Outlook version Storage location
Outlook 2013–2021 / Microsoft 365 Documents\Outlook Files
Windows 10/11 C:\Users<Name>\AppData\Local\Microsoft\Outlook
Older Versions (<2010) Documents and Settings\…\Microsoft\Outlook (his­tor­ic­al)

The easiest way to find PST files is directly in Outlook:

  • File > Account Settings > Account Settings
  • Select the ‘Data Files’ tab
  • Click ‘Open File Location’

To find all backup files, you should show hidden files and folders.

Note

If you don’t want to archive emails right away but often send or delete messages too quickly, Outlook can help you limit the damage. Restoring deleted emails in Outlook is easy.

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