OST File Synchronization Error

How to Fix "Unable to Expand...." OST file Synchronization Error

Microsoft Outlook OST file may get corrupt due to different reasons, such as the crash of MS Exchange Server, corruption of MS Exchange database, virus infection, failure of the hard disk drive, sudden system shut down, abrupt handling of MS Outlook, and more. Whatever the reason is behind the damage of the OST file, you will see the below error message when you will try to access its data from your Outlook account:

"Unable to expand the folder. The set of folders could not be opened. Errors could have been detected in the file xyz.ost. Quit all mail-enabled applications, and then use the Inbox Repair tool."

In the above error message, xyz.ost is the name of the OST file associated with your Outlook profile.

How to Resolve "Unable to Expand..." OST file Synchronization Error

After looking at the aforementioned error, you may think that everything stored in the OST has been lost. If this is the case, do not worry because here you will know the process to fix the corrupt OST file / resolve the aforementioned error message. Follow the steps given below:

  • Exit all applications of MS Office.
  • Navigate to the location where the corrupt OST file is stored. You can use Windows search function to locate the OST file.
  • Create a copy of the OST file.
  • Delete the original OST file that was showing the error message.
  • Restart Outlook.
  • Go to Send/receive and synchronize Outlook with Exchange Server. If there is no synchronization error and your account is available on the Exchange Server, then a new OST file will be created automatically.

In case, these steps do not resolve the "Unable to Expand...." OST file Synchronization Error, then you will have to repair the OST file and convert it into a PST file using an advanced OST to PST converter. Once you have a good OST to PST Converter installed in your computer, perform the below steps:

  • Launch the converter.
  • Browse the corrupt OST file.
  • Scan the OST file.
  • Save the data recovered from the OST file as a PST file. Now, you have a PST file, which you can open with MS Outlook.
  • Start MS Outlook and import the newly created PST file in it. You will access to all data that you had lost.
  • Now, you can activate the Offline Mode to create a new OST file. The new OST file will have work perfectly.

This way you can resolve the "Unable to Expand...." OST file Synchronization Error.