Repair Outlook Data Files (.pst and .ost)

If you cannot open your Outlook Data File (.pst), or you suspect that the data file is damaged, you can use the Inbox Repair tool (scanpst.exe) to diagnose and repair errors in the file. The Inbox Repair tool scans only Outlook Data Files (.pst or .ost) on your computer and analyzes the file structure integrity.

If you are using a Microsoft Exchange account and your offline Outlook Data File (.ost) is missing items or is not synchronized with the Exchange mailbox, you can re-create the file.

Inbox Repair tool (scanpst.exe)

Scanpst.exe is installed on your computer when you install Microsoft Outlook 2010. The Inbox Repair tool tries to correct any problems by resetting the data file structure and rebuilding the headers for Outlook items. If you are using an Exchange account, the tool does not connect to or analyze the data saved on the Exchange server.

IMPORTANT    You must exit Outlook before using the Inbox Repair tool. It is not accessible within Outlook.

1. Open Windows Explorer and select the drive:\Program Files\Microsoft Office\OFFICE14 folder.
2. Double-click Scanpst.exe.
3. In the Enter the name of the file you want to scan box, enter the name of the .pst or .ost file that you want to check, or click Browse to select the file.
4. To specify the scan log options, click Options, and then click the option that you want.
5. Click Start.
6. If errors are found, you are prompted to start the repair process to fix the errors.
   A backup file is created during the repair process. To change the default name or location of this backup file, in the Enter name of backup file box, enter a new name, or click Browse to select the file that you want to use.
7. Click Repair.
8. Start Outlook with the profile that contains the .pst file that you tried to repair.
9. In the Navigation Pane, click Folder List.
   Keyboard shortcut  To open switch to the Folder List, press CTRL+6.
   In the Folder List, you might see a folder named Recovered Personal Folders that contains your default Outlook folders or a Lost and Found folder. The recovered folders are usually empty, because this is a rebuilt .pst file. The Lost and Found folder contains the folders and items recovered by the Inbox Repair tool.
   You can create an Outlook Data File (.pst), and drag the items in the Lost and Found folder into the new data file. When you have finished moving all the items, you can remove the Recovered Personal Folders(.pst) file, including the Lost and Found folder, from your profile.

NOTE   

• If you are able to open the original Outlook Data File (.pst), you may be able to recover additional items from your damaged .pst file. By default, the Inbox Repair tool creates a file with the same name, but with the file extension of .bak. The .bak file is located in the same folder as your original .pst file. You may be able to recover items from the .bak file that the Inbox Repair tool could not recover. Make a copy of the .bak file, and give the file a new name with a .pst extension, such as bak.pst. Import the bak.pst file, and then move any additional recovered items to the new .pst file that you created.
• A copy of the log file is saved to the same folder as the .pst file.

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Re-create an offline Outlook Data File (.ost)

Offline Outlook Data Files (.ost) are copies of your Exchange information. It is not necessary to back up this file. You can create a new copy at any time.

1. Exit Outlook.
2. In Control Panel, click or double-click Mail.
   Where is Mail in Control Panel?
   Mail appears in different Control Panel locations depending upon the version of the Microsoft Windows operating system, Control Panel view selected, and whether a 32- or 64-bit operating system or version of Outlook 2010 is installed.
   The easiest way to locate Mail is to open Control Panel in Windows, and then in the Search box at the top of window, type Mail. In Control Panel for Windows XP, type Mail in the Address box.
   NOTE    The Mail icon appears after Outlook starts for the first time.
   The title bar of the Mail Setup dialog box contains the name of the current profile. To select a different existing profile, click Show Profiles, select the profile name, and then click Properties.
3. On the E-mail tab, select the Exchange account, and then click Change.
4. Clear the Use Cached Exchange Mode check box.
5. Click More Settings.
6. On the Advanced tab, click Offline Folder File Settings.
7. Click Disable Offline Use, and then in the dialog box that appears, click Yes.
   NOTE    If you cannot click Disable Offline Use, this indicates the Use Cached Exchange Mode check box was not cleared in step 4. This check box must be cleared.
8. Again, click Offline Folder File Settings.
9. Click OK.
10. In the dialog box that appears, click Yes.
11. Under Cached Exchange Mode Settings, select the Use Cached Exchange Mode check box.
12. Click OK, click Next, and then click Finish.
13. In the Account Settings and Mail Setup dialog boxes, click Close.

https://support.office.com/en-in/article/Repair-Outlook-Data-Files-pst-and-ost-25663bc3-11ec-4412-86c4-60458afc5253