How to fix common problems with Outlook .pst and .ost data files

If your data files in Outlook won’t open or get corrupted, or items appear to be missing in your inbox, you can use these steps to resolve the issues.

The desktop Outlook app uses two types of data files to store local copies of your emails, calendars, contacts, and other items, to allow you access to your information without an internet connection.

If you’re using an Outlook.com, Outlook 365, or Exchange account, this information is stored in an Offline Outlook Data File using a .ost format. However, if you’re using a POP or IMAP account like those you get from an Internet Service Provider (ISP), your information will be stored in an Outlook Data File using a .pst format instead.

Typically, you can go for a long time without any problems, but sooner or later, these files may stop working, and they can get damaged, which is why Outlook includes the Inbox Repair tool to diagnose and repair common errors with .pst files, as well as a mechanism to recreate .ost files automatically.

In this Windows 10 guide, we walk you through the steps to repair the data files when they’re damaged, items are missing in your inbox, or when a data file just won’t open in Outlook 2016 or previous versions.

• How to fix an Offline Outlook Data File (.ost)
• How to fix an Outlook Data File (.pst)

How to fix an Offline Outlook Data File (.ost)

If you have an Outlook.com, Outlook 365, or Exchange account, you can follow these steps to fix problems with a .ost data file in Outlook:

1. Close Outlook.
2. Open Control Panel.
   • Quick Tip: If you’re only using the default profile named “Outlook,” you can use the path %LOCALAPPDATA%\Microsoft\Outlook to go directly to the location of the .ost file, and then jump to step No. 13. Otherwise, continue with the steps below.
3. Click on User Accounts.
4. Click on Mail.
5. Using the Mail Setup experience, click the Show Profiles button.
6. Select the profile with the account you want to fix. (In Outlook 2016 the default profile is called “Outlook.”)
7. Click the Properties button.
8. Click the Email Accounts button.
9. Click on the Data Files tab.
10. Select the account to be repaired.
11. Click the Open File Location button.
12. Before you continue, make sure to close the “Accounts Settings,” “Mail Setup,” and “Mail” windows.
13. Right-click the .ost file for the account with problems, and select Delete.

Once you complete these steps, open Outlook again to automatically create a new .ost files for that particular account.

How to fix an Outlook Data File (.pst)

If you have an account connected using POP or IMAP settings, you can use the following steps to fix problems with a .pst data file:

1. Close Outlook.
2. Open File Explorer (Windows key + E).
3. Browse the following path: C:\Program Files (x86)\Microsoft Office\root\Office16
   • Important: If you’re using Outlook 2013, use the path C:\Program Files (x86)\Microsoft Office\Office15. If you have an older version of the app, change “Office15” in the path to “Office14” for Outlook 2010, or to “Office13” for Outlook 2007.
4. Inside the folder, find and double-click the SCANPST.EXE file.
5. Click the Browse button and locate the .pst file you want to repair.
6. Click the Start button.
7. Click the Repair button.

Once you complete these steps, the wizard will create a backup, proceed with the repair and create a log file with information about the repair process.

After the repair is complete, you can start the Outlook app associated with the data file.