Data Backup Problems

How to Back Up an Outlook OST File on Windows 11

Camila Milosovich Sep 30, 2026 868 views

Question details

The user needs to know how to back up an Outlook OST file securely on Windows 11 for data recovery and safe storage.

How to Back Up an Outlook OST File on Windows 11

Product: Microsoft Outlook
Device & OS: Windows 11
Scenario: Attempting to create a reliable and portable backup of mailbox data, particularly for IMAP accounts containing local-only items.
Observed behavior: OST files are synchronized copies tied to a specific Outlook profile and cannot be easily copied as a reliable backup. Mailbox data must be exported to a PST format instead.

Before you start

Before exporting your mailbox data, verify that Microsoft Outlook is online and fully synchronized with your mail server so that no recent emails or calendar events are missing from your final backup.

Solution 1Recommended

Export Mailbox Data to a Portable PST File

Since an OST file is tied to your specific Outlook profile, the correct and most reliable way to back up your data is by exporting it to a PST file.

A PST (Personal Storage Table) file is a portable backup format that can be easily imported into any Outlook profile or moved to another computer. This is critically important for IMAP accounts that contain folders marked '(This computer only)'.

Open Export Settings

Launch Microsoft Outlook. Click on the 'File' tab in the top-left corner of the window, then select 'Open & Export' from the left-hand menu.

Start the Wizard

Click the 'Import/Export' button to launch the Import and Export Wizard.

Choose the Export Option

Select 'Export to a file' from the list of actions and click 'Next'.

Select the PST Format

Choose 'Outlook Data File (.pst)' as the file type you want to create and click 'Next'.

Select Folders to Back Up

Select your email account at the top of the hierarchy to back up everything, or choose specific folders. Ensure the 'Include subfolders' box is checked, then click 'Next'.

Save the PST File

Click 'Browse' to choose a location on your Windows 11 drive to save the file. Provide a recognizable file name, select your preferred duplicate item handling option, and click 'Finish'.

Export Mailbox Data to a Portable PST File

Avoid Direct File Copying: Simply locating and copying the raw .ost file from your AppData folder is not a valid backup method, as it generally cannot be opened outside the exact Outlook profile that originally created it.

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1. Download and Install: Get the free WPS Office installer from the official website and run it on your Windows 11 PC.
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Frequently Asked Questions

Can I just copy my OST file to an external drive as a backup?

While you can physically copy the .ost file to an external drive, it is generally useless as a backup. OST files are encrypted and inextricably tied to the specific Outlook profile and Windows account that created them. You must export the data to a .pst file to ensure it can be restored.

What does '(This computer only)' mean next to my Outlook folders?

This label appears in IMAP email accounts for folders like Contacts, Calendars, or Tasks that do not synchronize with your mail server. If your OST file gets corrupted or deleted, the data in these specific folders is permanently lost unless you regularly export them to a PST file.

Where is the default location of the OST file on Windows 11?

By default, Outlook saves OST files in your local AppData folder, typically found at C:\Users\[YourUsername]\AppData\Local\Microsoft\Outlook. However, you should use the Import/Export wizard rather than attempting to interact with this file directly.

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