Outlook OST Is In Use And Cannot Be Accessed-[Fixed]

Microsoft and the Exchange Servers are the widely used popular and top-ranked applications. MS Outlook stores its mailbox items like email, contacts, calendars, etc, in the OST file format which is also known as Offline Storage Table. But at some point, Outlook users face “OST is in use and cannot be accessed” error. If you are one of them then follow this content from top to end to fix your issue without any extra effort.

Causes for “xyz.ost is in use and cannot be accessed” Error

This error can occur when a user tries to send and save Office application functions such as MS Word, Powerpoint. When this error occurs in Outlook, it creates a file opening issue and due to this, your “Outlook OST cannot be opened” problem comes in occurrence. This problem is hard to find but not impossible to get. This error may also occur due to several other reasons like:

  • Communication and synchronization problem between the OST and Associate Exchange Servers.
  • Downloaded the application in the wrong way and hence caused conflicts.
  • Many of you want to request to access the same OST file at the same instant of time.
  • Due to interrupted or slow connections of your internet.
  • Other processes like the Office Communicator, LYNC and UCMAPI run in the background.

Let’s move to know all the possible methods by which you can Fix this Outlook Error. You can also fix this by converting OST to MSG format.

Methods to fix Outlook Error Out

ost is in use and cannot be accessed

There are many methods to rectify your “Outlook OST cannot be opened” error. What you need to do is follow the instructions given below:

Quit All Process Like MS Outlook – Check whether multiple files of the same task or the files related to OST are running as they think that the files are in use and they will show you this error message. To end up all these tasks follow the below steps:

  • Firstly, get out from Outlook.
  • Open task manager.
  • Go to the “Processes” tab seen on the many tabs of the Task Manager.
  • From the many applications running on your PC search for Outlook, LYNC, Communicator, or UCMAPI named processes.
  • One by one choose that running task and then click on the End Task button.

Disable all the Exchange Cached files – Sometimes a user will get this error due to the saved cached files of your Exchange servers that will show the Outlook files in use and hence the user will get this error. Follow the steps to disable cached files:

  • Initially, exit Outlook.
  • Open Control Panel.
  • After that, move to Mail option.
  • In the mail option select Email Accounts and finally on Email option.
  • Then select your desired email-id and then press the Change button.
  • Remove the tick-mark from “Use Cached Exchange Mode”.
  • Press the Next button.
  • Finally hit on the Finish button.

These are the manual procedures that you can perform to remove this error completely. But always keep in mind that there may be some data loss during the process. As there are many limitations to this approach that you must know.

Limitations of Manual Methods:

    • You cannot perform the steps quickly as it takes more time for steps execution.
    • Technical knowledge must be known.
    • If one step skips by chance, then again have to repeat the steps from the first one.
    • Complex process.

So, on looking over the above limitations, you must be thinking of another method that quickly resolves the problem. Therefore, use the below mentioned utility for fixing the issue immediately.

Use Third-Party OST Converter Tool

One can easily convert their OST files into the PST files that can remove the problem that comes in the case of OST i.e, OST is in use and cannot be accessed. By using the third-party OST converter you can resolve many problems with a single pack. Some features of third-party OST Converters are:

  • It allows you to perform OST Conversion safely & speedily in just no time.
  • Users can also export their OST mailbox data into Windows Live Mail (EML) with ease.
  • One can transport their OST Emails into Mac Mail i.e, on MBOX very efficiently.
  • It is easy to export attachments in go like emails, contacts, calendars, tasks, notes, journals, etc. from OST data files into Outlook PST data files.


Outlook is one of the most popular applications of all time but also users will face some errors in this utility too. Users will find an error like OST is in use and cannot be accessed error due to many reasons as we discussed above. Also, in this technical guide, we discussed how we can fix this error step by step with ease. It is a wise decision to use a third-party utility to solve this issue.

About: Nisha Yadav