What a PST file is and why you have one

A PST file is Outlook's way of storing your email, calendar, contacts, and tasks in a single file on your computer. The letters stand for "Personal Storage Table." When you back up your Outlook data, export messages to save them separately, or receive someone else's archived email, you end up with a .pst file — a file whose name ends in those three letters.

PST files are not automatically part of Outlook. They exist because you (or someone else) created them deliberately. Your regular Outlook inbox lives in a different location — either on Microsoft's servers if you use Outlook.com or Microsoft 365, or in a local folder if you use Outlook with an older email account. A PST file is a backup or archive you can move around, share, or restore later.

Key Takeaways

  • PST files open inside Outlook through the File menu, not by double-clicking the file itself.
  • You need the same version of Outlook (or newer) that created the PST file, or the file may not open.
  • Once opened, the PST file appears as a folder in your Outlook sidebar and you can read, search, and copy messages from it.
  • If Outlook refuses to open the file, run the Inbox Repair Tool (scanpst.exe) to fix corruption before trying again.

Opening a PST file in Outlook on Windows

Do not double-click the PST file. Open Outlook first, then tell Outlook to open the file. In Outlook, go to File at the top left, then select Open & Export, then choose Open Outlook Data File. A window will appear asking you to find the file on your computer. Navigate to wherever the PST file is stored, select it, and click Open.

The PST file will now appear in your Outlook sidebar as a folder. You can expand it to see the emails, calendar events, contacts, or tasks inside. You can read messages, search within the PST file, and copy items back into your main Outlook folders if you need them. The file stays open as long as Outlook is running.

If the file is very large (over 2 gigabytes), Outlook may take a minute or two to load it. Do not close Outlook during this time. If Outlook crashes or freezes when you try to open the file, the PST file may be corrupted — see the section below on repairing it.

Opening a PST file in Outlook on Mac

Mac versions of Outlook handle PST files differently than Windows does. Go to File, then Import, then select Outlook Data File. Choose the PST file from your computer. Outlook will import the contents into your main Outlook folders rather than keeping the PST as a separate folder you can see in the sidebar.

This means the emails, contacts, and calendar events from the PST file merge into your existing Outlook data. If you want to keep the PST file's contents separate and organized, import it into a new Outlook account or folder first, rather than importing it directly into your main account.

Version mismatches and when a PST file will not open

Outlook has many versions: Outlook 2010, 2013, 2016, 2019, Microsoft 365, and others. A PST file created in an older version of Outlook usually opens in a newer version without trouble. A PST file created in a newer version often will not open in an older version — Outlook 2010, for example, cannot read a PST file created in Outlook 2019.

If you receive a PST file from someone else and Outlook refuses to open it, ask them which version of Outlook they used to create it. If it is newer than yours, you will need to update Outlook or use a different computer that has a newer version installed. If you are unsure which version you have, open Outlook, go to File, then Office Account (or About Outlook on Mac), and look for the version number.

Repairing a corrupted PST file

If Outlook crashes, freezes, or shows an error message when you try to open a PST file, the file may be corrupted. Windows includes a built-in repair tool called the Inbox Repair Tool (scanpst.exe). On Windows, press the Windows key and type "scanpst" to find it, or navigate to your Outlook installation folder and look for scanpst.exe.

Run the tool and point it to the PST file you want to repair. The tool will scan the file and offer to fix any problems it finds. This process can take several minutes for large files. Once the repair is complete, close the tool and try opening the PST file in Outlook again.

Mac does not include a built-in repair tool. If a PST file is corrupted on Mac, your options are limited: you can try importing it anyway (Outlook may recover some data), or you can use a third-party repair tool. Some of these tools cost money. If the PST file is important and repair fails, consider reaching out to the person who created it to ask for a fresh copy.

Moving or backing up a PST file safely

PST files are just regular files on your computer, so you can copy them, move them, or back them up like any other file. However, never move or delete a PST file while Outlook is open and the file is loaded. Close Outlook first, then move or copy the file, then open Outlook again.

If you move a PST file to a new location on your computer, Outlook will not automatically find it. You will need to open it again using the File menu method described above. If you want Outlook to remember where the file is, keep it in the same location or update the file location in Outlook's settings after you move it.

When to use a PST file versus Outlook's built-in backup

Creating a PST file manually is useful if you want to archive old emails, share your inbox with someone else, or back up your data before switching computers. However, if you use Microsoft 365 or Outlook.com, your email is already backed up on Microsoft's servers — you do not need a PST file for safety.

If you use Outlook with an older email account (like a corporate Exchange server), your data may not be backed up automatically. In that case, creating a PST file periodically is a good idea. You can set Outlook to create a backup automatically, or you can do it manually whenever you want. The PST file gives you a copy you control, separate from your email provider's servers.

Frequently Asked Questions

Can I open a PST file without Outlook installed?

Not easily. PST files are designed for Outlook. Some third-party tools claim to read PST files without Outlook, but they are not reliable and may not show all your data correctly. The safest approach is to install Outlook or use a computer where Outlook is already installed.

What if the PST file is password-protected?

Outlook does not password-protect PST files natively. If someone told you a PST file is password-protected, they likely encrypted the file itself using Windows or a third-party tool. You will need the password to decrypt it before Outlook can open it. Ask whoever created the file for the password.

Can I open a PST file on my phone or tablet?

No. PST files only work with Outlook on Windows or Mac. Outlook on phones and tablets does not support opening PST files. If you need to access the data from a phone, you would need to import the PST file into your main Outlook account first, then sync that account to your phone.

How do I know if a file is actually a PST file?

Check the file name. A PST file always ends in .pst. On Windows, you may need to turn on the option to show file extensions. On Mac, right-click the file and select "Get Info" to see the full file name and type. If the file name does not end in .pst, it is not a PST file and Outlook will not open it.

What is the difference between a PST file and an OST file?

An OST file (Offline Storage Table) is created automatically by Outlook when you use certain email accounts. It stores a copy of your email on your computer so you can read it offline. A PST file is something you create manually. You should never try to open an OST file directly — Outlook manages it automatically in the background.