How to Fix the “Outlook OST file cannot be opened Windows 10”?
Outlook data file error message, “The file xxx.ost file cannot be opened,” may appear all of a sudden while accessing or opening an Outlook account in Windows 10. The error indicates a problem with the Offline Outlook data file (.OST), due to which the OST file became inaccessible.
When you click ‘OK,’ the Outlook Data File error message closes, but the Outlook application does not open. Thus, you cannot access your Outlook account or mail items.
In this guide, we’ll be discussing the reasons of Outlook OST file cannot be opened error, along with the solutions to fix the error and get back access to the mail items stored in the inaccessible OST file.
Reasons for Outlook OST File Cannot Be Opened Windows 10 Error
The Outlook Data File error message may occur due to the following reasons:
- Damaged Outlook OST file
2. Corrupt Outlook program files
3. Abrupt system shutdown or power failure
4. Force close Outlook application
5. System crash
6. Sync errors between Exchange mailbox and OST
7. Outlook profile deleted from the server
8. Virus or malware intrusion
How to Resolve the ‘Outlook OST File Cannot Be Opened’ Error?
To resolve the Outlook OST file that cannot be opened an issue, you can recreate the OST file by deleting the inaccessible OST. However, the newly created OST file may not contain your offline data or completed work. Thus, it can lead to data loss. Further, the new OST file may take a few minutes to couple of hours, depending on the mailbox size, to finish synchronization and update the mailbox.
You may fix the OST using SCANPST.EXE or convert the inaccessible OST file to Outlook importable PST format using a reliable OST to PST converter software, such as Stellar Converter for OST.
The software allows you to scan, access, preview, and then save the mailbox items from an inaccessible or orphaned OST file to a new PST file. After the conversion, you can import the PST file to your Outlook account via Outlook Import/Export wizard and restore the mailbox items.
These methods are explained in detail below.
Method 1: Disable Cached Exchange Mode
You may choose to run Outlook in Online Mode and fix the issue. For this, you need to start Outlook in safe mode and then disable the Cached Exchange Mode. The steps are as follows:
- Press Windows+R, type outlook /safe and then click ‘OK’ or press ‘Enter’.
2. Now go to File > Info > Account Settings and then choose ‘Account Settings…’ from the available options.
3. Click on your Outlook email profile and then click ‘Change’.
4. Now unselect the Use Cached Exchange Mode checkbox and click ‘Next’.
5. Click ‘OK’ when the prompt appears and then click ‘Finish’.
After this, restart Outlook normally to access your mails. The performance might get slower as, unlike Cached Exchange Mode, Outlook in online mode requires continuously fetch and upload data.
Method 2: Use Inbox Repair Tool (SCANPST.EXE)
With SCANPST.EXE, you can try to fix the inaccessible Outlook OST file. However, the utility does not work with encrypted, severely damaged, or OST files larger than 2 GB. Follow these steps:
1. Open SCANPST.EXE. The location of this utility varies based on the Outlook and Windows version. You may find it at the following location on your system,
Outlook 2019 & 2016: C:\Program Files (x86)\Microsoft Office\root\Office 16
Outlook 2013: C:\Program Files (x86)\Microsoft Office\Office 15
Outlook 2010: C:\Program Files (x86)\Microsoft Office\Office14
Outlook 2007: C:\Program Files (x86)\Microsoft Office\Office 12
2. Click ‘Browse’ to select the OST file you intend to repair, and then click ‘Start.’
3. After the initial scan, the utility displays the repair option if errors are found. Ensure that ‘Make a backup of scanned file before repairing’ is selected. Then click ‘Repair’
4. Wait for the process to complete. After the repair is done, delete the associated.OST.tmp file located at
C:\Users\YourProfileName\AppData\Local\Microsoft\Outlook.
If this works, you don’t need to follow the next method to recreate the OST file. Instead, follow the last method to extract mailboxes from the OST file that may be missing after the repair.
Method 3: Recreate OST File
If you are using an Exchange, Outlook.com, or Office 365 account in MS Outlook, follow these steps to fix the problem with the.OST file:
- Close MS Outlook and then open Control Panel
2. Click on User Accounts > Mail.
3. Click ‘Show Profiles…’
4. Choose the Outlook profile and click ‘Properties.’
5. Click ‘Data Files…’
6. Select the email profile under the ‘Data Files’ tab and then click ‘Open file location.’ Also, close Account Settings, Mail Setup, and Mail windows.
7. Then right-click on the OST file, choose ‘Cut’ and then paste the file at some other location, preferably on a different volume or backup drive. You may also choose ‘Delete’ (not recommended).
8. Start Outlook to recreate the Outlook OST file that you want to repair. At this stage, Outlook should open.
Once Outlook opens, wait for synchronization to finish and then check your mail items. If the mail items are missing, you can follow the next method to extract the mail items from your inaccessible or damaged OST file to PST and then import it to your Outlook account. This will restore your missing mailbox items.
Method 4: Convert Inaccessible OST File to PST
To convert inaccessible or damaged OST files to Outlook importable PST files, follow these steps.
- Download, install and launch Stellar Converter for OST software on Windows PC.
2. Click ‘Browse’ to choose the inaccessible OST file and click ‘Convert.’
3. After the scan, the software displays all mailbox items extracted from the inaccessible OST file. You can click on any mail item to see its enhanced preview and then select the item or folder for saving.
4. Click ‘Save Converted File’ in the Home menu. A Save As dialog box appears.
5. Choose ‘PST’ and then click ‘Browse’ to choose a save location.
6. Click ‘OK’ to start saving the mailbox items extracted from the inaccessible OST file to a new Outlook importable PST file.
Now you can import this PST file into your profile, set up in Outlook 2019, 2016, 2013, 2010, or 2007 via Import/Export wizard.
Conclusion
Inaccessible or damaged OST file can cause various errors, such as Outlook OST file cannot be opened, that can disrupt the email communications. Users facing such errors cannot access or open their configured Exchange, Outlook.com, or Office 365 accounts.
The damage may occur due to various reasons mentioned in this guide. If your Outlook OST cannot be accessed, follow this guide to resolve the problem quickly.
You may also extract the mail items from such OST files with ease by using an OST to PST converter software, such as Stellar Converter for OST. The software helps you save time, avoid data loss, and restore all mail items from inaccessible or orphaned OST files.
