What Is a PST File in Outlook?

In Microsoft Outlook, a PST file is a data file that stores items such as email, contacts, calendar appointments, tasks, and notes on a computer. PST stands for “Personal Storage Table.” People use these files to keep a copy of Outlook data on their computer. They also save older items or move data between computers.

A PST file is useful when you need an archive you can open in Outlook or when your account uses POP, which downloads email to your device. Your PST file is separate from your email account settings. You are responsible for protecting and backing up the copy stored on your computer. Microsoft describes what Outlook data files contain and how people use them.

How a PST file differs from an OST file #

A PST file holds Outlook data that you can open separately in Outlook. An OST file is an offline copy that Outlook synchronizes with an email account, such as a Microsoft Exchange or Microsoft 365 mailbox. If you remove an OST file, Outlook can generally recreate it by syncing with the account; a PST file holds its own stored data and should be preserved if you need its contents.

Which file type you see depends partly on how you set up your email account. Microsoft says POP accounts store information in a PST file. With Microsoft 365, Exchange, and Outlook.com accounts that do not use POP or IMAP, you typically will not have a Personal Folders PST file because the email remains on the server. See Microsoft’s instructions for finding and transferring Outlook data files.

When to use a PST file #

Use a PST file to keep older messages out of your active mailbox or to save an Outlook archive on your computer. For example, you might move older email into a PST to reduce the amount of mail in your mailbox. A PST can also help carry locally stored Outlook items to another computer.

Moving the file does not move your email account settings. You still need to set up the account on the new computer, then open the PST in Outlook to access the items it contains. On Windows, Microsoft lists Documents\Outlook Files as a common location, but the actual folder depends on your Outlook and Windows versions and on how the file was created.

Opening a PST in new Outlook #

Outlook for Windows has two versions: classic Outlook and new Outlook. Microsoft’s support page says new Outlook supports opening PST files and working with their messages and folders, including moving, copying, and deleting items. It also describes exporting mailbox data to a PST. Which features are available depends on your Outlook version and setup.

For new Outlook to open a PST, Microsoft says classic Outlook must also be installed, and both versions must use the same 32-bit or 64-bit architecture. PST files are not supported in the ARM version of new Outlook. Check Microsoft’s current PST support requirements if a file will not open or an option is missing.

Protecting and backing up a PST #

A PST file on a laptop, external drive, or network location can be lost or exposed if the device or location is lost, stolen, or poorly protected. Back up the file somewhere separate from the computer that holds it, and avoid treating a PST as the only copy of important mail. Large PST files can also slow OneDrive syncing and trigger messages such as “Processing changes” or “A file is in use,” according to Microsoft’s transfer guidance.

$ curl -fsSL https://raw.githubusercontent.com/vincentsch/mailmd/main/install.sh | sh

Set up mailmd so you can read my email. Use https://github.com/vincentsch/mailmd: read its AGENTS.md and follow the steps. Connect my mailbox and run the first sync. Then show me where the files are.