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Default Outlook Profile.ost Cannot be Accessed / Opened When in Use?

Published By Ashwani Tiwari
Tej Pratap Shukla
Approved By Tej Pratap Shukla
Published On December 31st, 2021
Reading Time 5 Minutes Reading

Summary – Are you getting Default Outlook Profile.ost cannot be opened error while using Microsoft Outlook 2016, 2013, 2010, 2007? Are you looking for a reliable solution but can’t get one? No need to worry as we have come up with a solution which will help you to resolve default Outlook profile.ost is in use and cannot be accessed error in an efficient way.

A large number of users who are familiar with Microsoft Exchange and Outlook might have knowledge of what OST file is. For those who don’t know, the OST file is a data file which stores all the Outlook mailbox data in it. The file is stored on the local machine in which entire email messages, contacts, calendar, etc. are stored. Whenever the Outlook gets connected to Exchange, all the file changes are synchronized to the mailbox server.

Though, while using Microsoft Outlook, some of the users encounter an error message stating that Default Outlook Profile.ost cannot be opened. It means that whenever a user tries to access Outlook, it throws an error and that user cannot use Outlook until the issue is fixed. Therefore, it becomes really important to resolve the error immediately so that the email communication of the users is not affected. But, before directly going to the solution, it is essential to know the reasons behind the message.

Important Note: If you want to resolve the issue without wasting any time and as quickly as possible, you can go for the expert-recommended solution.

Major Causes of Default Outlook Profile.ost Cannot be Opened Issue

There could be many possible reasons which can be possible for the above-stated error. But, some of the most common causes are listed in the following section:

  • This error can occur if there is improper synchronization between Microsoft Outlook and Exchange Server.
  • At times, some software conflicts can also be the cause behind default Outlook profile.ost is in use and cannot be accessed.
  • Slow or unreliable internet connection can also be the reason for this issue.
  • If the OST file which you want to access is in use by some other program, then also the email application can display this prompt message.

Various Methods to Fix Default Outlook Profile.ost Cannot be Accessed / Opened

Method 1 – Terminate All Outlook Related Tasks

Initially, the users can try implementing the following steps to eliminate the error:

  1. First of all, close the Outlook window running on your system.
  2. Then, open Task manager.
  3. Here, select the Processes tab from the window.
  4. Now, find “Lync”, “Communicator”, “UCMAPI” or “Outlook” in the processes window.
  5. Once you search these running processes, close them by clicking on End Task button.

Method 2 – Disable the Cached Exchange Mode

Another method using which the users can resolve default Outlook profile.ost is in use and cannot be accessed issue is by turning off the Cached Exchange Mode. Execute the below-mentioned steps to do the same:

  1. To start with it, close Microsoft Outlook.
  2. Go to Control Panel >> Mail option.
  3. Now, click on Email Accounts >> Email tab.
  4. Here, choose the Email ID and then click on Change button.
  5. In this window, you can uncheck the “Use Cached Exchange Mode”.
  6. Finally, click on the Next button and then Finish button to complete the process.

Method 3 – Run ScanPST.exe Utility

If all these methods fail to eliminate the Default Outlook Profile.ost Cannot be Accessed / Opened error for you. Then, there might be chances that the OST file which you are trying to access is corrupted or damaged. Thus, this utility can help you to remove the corruption from the file. You just have to perform the following steps:

  1. In the initial step, run the scanpst.exe utility.
  2. Now, press the Browse button to search for the damaged OST file.
  3. Click on the Start button to initiate the scan process.
  4. The utility will start generating a list of errors.
  5. After completion of the scanning process, click the Repair button to fix the issues.
  6. Once it gets completed, start Outlook again.

Remove Default Outlook profile.ost is in Use and Cannot be Accessed in an Efficient Way

The users can try all the above mentioned manual procedures to resolve the issue. But, these methods have some limitations and it is not guaranteed that the users will successfully eliminate the error. Therefore, we have come up with a reliable solution i.e. Outlook OST to PST Converter which will help users to convert their OST file into Outlook accessible PST format. After the successful conversion, the users can import that file into any Outlook application.

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Moreover, the software also maintains the exact structure of the emails as it was before in the OST file. Also, the inbuilt utility only allows users to remove a minimal level of corruption. Thus, if the OST file is severely damaged then scanpst.exe fails to repair the file. So, this third-party application proves to be the best solution as it overcomes all the limitations faced in the manual procedures.

How to Fix Default Outlook Profile.ost Cannot be Accessed Issue Using the Software?

Following steps are how you can solve the issue:

Step 1 – Download the software for conversion and click on the Add File option.


Step 2 – Navigate the file you want to convert and hit Open.


Step 3 – Hit on the Export button after previewing the data.


Step 4 – Choose PST as export type, Browse for destination path and press Export.



The OST file holds a great importance for Microsoft Outlook. If it gets inaccessible due to any reason, then it can stop the email communication of the users and they cannot access their mailbox data. One such error is Default Outlook Profile.ost Cannot be Opened / Accessed. There are some manual methods which are available to fix the issue of the users. But, there are some limitations associated with them. So, the third-party utility is always suggested to have a secure and reliable solution.


By Ashwani Tiwari

I am an Expert Technical Analyst, specialized in assisting users with complex technological challenges. Through my blogs and articles, I offer expert guidance to help tackle these technical issues effectively. My true passion lies in providing valuable insights and simplifying complicated technicalities, enhancing user understanding and confidence.