Troubleshoot "Unable to Expand the Folder" Error of MS Outlook

Microsoft Outlook utilizes two forms of extensions to save mailbox information on your operating system. One is the OST file and other is the PST file. Offline storage file (.ost) is utilized when you are using Outlook with Exchange Server. All work which is done in offline mode (where there is no internet facility) is being saved in OST document and gets synchronized when internet is connected with Exchange workstation.

If you make an effort to access your MS Outlook but it fails to synchronize the offline storage table (.ost) file and display following error message:

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

Related Article: Reasons of OST File Corruption

You may receive this error message implies there is some problem with your OST Document and it couldn't get appropriately synchronized with the Exchange Server and that results in inaccessibility of the OST file. There are various reasons behind OST file corruption:

  • OST gets corrupted by Trojan infection.
  • Virus assaults on Exchange Server.
  • Exchange Server Collapse.
  • Accidental lost of Exchange Mailbox.


As expressed in the error message, quit all mail empowered applications that can utilize OST document.

  • Locate the OST record: A point by point clarification of where to discover Outlook OST document.
  • Run the Inbox Repair utility to repair the OST record.
  • Recover the repaired items.

In a few situations sacnpst.exe does not repair offline storage (OST) file this is because of the way that this utility does not works in difficult instances of OST document corruption. In case this technique unsuccessful you ought to attempt Third party OST Recovery Software that transforms OST file to PST document. Such mechanisms are fit for changing over OST to PST document even in most astonishing level of OST corruption and ready to recuperate all segments of OST document, for example, emails, messages with attachments, connections, contacts, tasks, calendar, journals and notes etc. When you get the changed over PST document you can store it to any drive and can access it straightforwardly with MS Outlook.

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