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Resolved ‘Outlook OST File Cannot Be Opened’ Error


Microsoft Outlook is a robust email client that is acclaimed for its advanced features like security, compatibility with the MS Office suite, and efficient email management capabilities. That is why it is widely preferred for Microsoft Exchange, Microsoft 365, and IMAP/POP3 email account users.

Even though Outlook is widely used by global businesses, it is prone to errors that may be frustrating and time-consuming to resolve. ‘Outlook OST file cannot be opened’ is one of the most widely searched queries by users. This issue pops up after a specific event, like an Outlook upgrade or reinstallation, when data files become orphaned or inaccessible.

This post revolves around how to fix Outlook OST File errors, how to convert OST to PST file. It will also put ScanPST.exe, which is also known as the Inbox Repair Tool, in the spotlight. 

What Causes ‘Outlook OST File Cannot Be Opened’ Error?

There are many factors that cause ‘Outlook OST file not Opened’ issue. This error may occur owing to file corruption, synchronization issues, malware infections, software conflicts, and hardware failures. Below are some common causes for this error:

  • OST File Corruption Issue: The OST (Offline Storage Table) stores a cached copy of your Exchange Server mailbox. It is used for offline access to your email, calendar, and other data in Microsoft Outlook. Any damage or corruption in these OST files may cause ‘Outlook OST File Not Opened’ error.
  • Synchronization Issues: Incomplete synchronization processes prevent the OST file from updating properly. This problem can lead to errors in opening the OST file.
  • Improper Shutdown of Outlook: If Outlook closes suddenly owing to system shutdown or termination of processes, it can fail to update mailbox folders. It can lead to the OST file corruption. 
  • Malware Infection: Any virus attack on your system can damage the OST file, leading to errors when trying to open it. 
  • Profile Corruption: Your Outlook profile may become corrupted following a ransomware attack that can lead to the OST file corruption. To resolve this issue, you may have to rebuild the Outlook profile.
  • Misconfiguration of Outlook Settings: Incorrect Outlook Configuration like incorrect profile, or server settings can prevent the OST file from being opened.
  • Hardware Issues: Any problem with the storage device where OST file is stored, such as a hard drive failure or bad sectors, can result in the OST file corruption.
  • Outdated Version of Outlook: If you attempt to access an OST file generated in a newer Outlook version in an older version, you may encounter this error.

How to Resolve ‘Outlook OST File Cannot Be Opened’ Error? 

Orphaned or corrupted file is the main reason of ‘Outlook OST file not opened’ error. Such files are created due to improper synchronization with your Exchange mailbox server. You can try the below solutions if you are unable to open the .ost file in Windows 10, 11, 8 and 7. 

I: Exit Outlook & Related Processes:

Step 1: Close Outlook on your computer:

  • Click on the “File” tab in the top-left 
  • Select “Exit” or “Close Outlook” from the dropdown menu
  • Alternatively, press Alt + F4 while Outlook is active to close the application

Step 2: Close any Outlook-Related Processes: 

  • Navigate to the Task Manager
  • Search any processes with word ‘Outlook’ like ‘Communicator’, ‘Lync’, ‘UCMAPI’ or ‘Outlook.exe’.
  • Click on each of these processes
  • Press the ‘End Task’ button to close them
  • After closing all processes, close the Task Manager

Step 3: Reopen Outlook

  • Open Microsoft Outlook
  • Verify if the application synchronizes emails with the server successfully

II: Repair OST File:

We can also resolve ‘Outlook OST file cannot be opened’ error by repairing the damaged OST file with Outlook’s built-in utility–ScanPST.exe. This utility is located in Outlook’s installation directory. Also known as the ‘Inbox Repair Tool’, it doesn’t connect to or analyse any data stored in an Exchange mailbox. This utility only looks for errors (corruption), and if there are any, gives you the opportunity to allow the tool to fix those errors. 

Follow the below steps to repair OST file with the Inbox Repair tool or ScanPST.exe.:

1. Exit Outlook and browse to one of the following file locations:

  • Outlook 2019: C:\Program Files (x86)\Microsoft Office\root\Office16
  • Outlook 2016: C:\Program Files (x86)\Microsoft Office\root\Office16
  • Outlook 2013: C:\Program Files (x86)\Microsoft Office\Office15
  • Outlook 2010: C:\Program Files (x86)\Microsoft Office\Office14
  • Outlook 2007: C:\Program Files (x86)\Microsoft Office\Office12


3. Select Browse to select the Outlook Data File (.pst) you want to scan

Note: A new log file is created by default during the scan. You can change settings so it doesn’t make this file or so it adds its findings to an existing one instead.

4. Choose Start to begin the scan

5. If the scan finds errors, choose Repair to start the process to fix them

Shows results of scanned Outlook .pst data file using the Microsoft Inbox Repair tool, SCANPST.EXE

Note: The repair process creates a backup file. If you want to change the name or location, you can change it by entering a new name 

6. When the repair process is finished, start Outlook with the profile associated with the Outlook Data File you just repaired

III: Convert OST to PST Files: 

Converting OST (Offline Storage Table) to PST (Personal Storage Table) is required to recover severally corrupted OST Files that cause ‘Outlook OST File Not Opened’ error. This conversion facilitates users to recover as much data as possible from the corrupted file. It allows access to the mailbox data stored within the OST file independently of the Exchange Server.

Convert OST to PST Using Import/Export Feature: Follow the below steps to convert OST to PST:

  • Launch Microsoft Outlook in the Cached Exchange Mode
  • Open Outlook 
  • Go to the “File” tab
  • Click on “Open & Export” 
  • Select “Import/Export”
  • In the Import and Export Wizard, choose “Export to a file” and click “Next”
  • Select “Outlook Data File (.pst)” and click “Next”
  • Choose the mailbox or specific folders you want to export
  • Specify the location and name for the PST file, and choose options for handling duplicates
  • Click “Finish” to start the export process

Are there some limitations of the Manual Conversion of OST to PST Files?

Well, like every tool, the conversion using the Import/Export feature, has its own pros and cons. This wizard will work only on accessible OST files, not on severally corrupted files. The main limitations of this method are listed below:

  • Complex for Non-Technical Users: Conversion using the manual method needs a level of technical expertise as it requires navigation through the Outlook’s interface and an understating export options. 
  • Limited Accessibility: Manual conversion is possible only for accessible OST files, not for severely corrupted or inaccessible ones.
  • Data Loss: There is a risk of the data loss, especially in cases where the OST file is damaged or if errors occur during the export process.
  • File Size Issues: The OST to PST conversion process may stop if the OST file size is large. 
  • Incomplete Data Export: Sometimes, the user may not be able to export all mailbox items, especially in cases where there is synchronization issue or there is some sort of data corruption issue within the OST file. 
  • No Automated Recovery: This process doesn’t provide automated recovery options for severely corrupted OST files.

Convert OST files to PST Using Software Method: 

As discussed above, there are some limitations to the Manual Method of converting OST to PST. But there are some specialized third-party tools that easily convert even the inaccessible, orphaned, and encrypted OST (Offline Storage Table) files into the PST (Personal Storage Table) format. Stellar Converter for OST is an award-winning tool that can help convert large-sized, inaccessible, or encrypted OST files into PST format. The software supports Outlook 2019, 2016, 2013, 2010, 2007, 2003, 2002, and 2000. Featuring a user-friendly interface, this tool also converts and saves file in other formats like PST, MSG, EML, RTF, HTML and PDF.

Benefits of Stellar Converter for OST:

  • Award-winning converter software
  • Free-trial version availability
  • Convert large OST (exchange & IMAP) files into PST – no file size limitation
  • Converts corrupted and encrypted OST into PST files
  • Convert and save file in PST, MSG, EML, RTF, HTML and PDF formats
  • Supports Outlook 2021, 2019, 2016, 2013, 2010, 2007, 2003, 2002, and 2000


In the above post, we have discussed how to resolve the ‘Outlook OST file cannot be opened’ error which is one of the most searched queries by users. Converting OST to PST is a common and effective method for resolving this issue. The conversion can be done manually using the Outlook Import/Export wizard. As discussed, there is a strong possibility that manual processes do not fulfil your expectations, as the manual method has some limitations. If such a scenario arises, we should use the specialized OST to PST Converter Tool, which is specifically developed to convert severally-inaccessible or orphaned OST file.

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