How to repair MS Outlook .OST files when its synchronization with Exchange Server fails?

What makes Microsoft Outlook the most preferred email client all around the globe is its Offline Working Mode feature. It keeps data in .OST files that serves as a backup and proves helpful in case of losing .PST files. All the mailbox items such as emails, notes, journals, calendar entries, contacts, tasks, posts, task requests, appointments, meeting requests, distribution lists, etc. are stored in Offline mode as well. It is just a replica of exact Exchange Server user mailbox and is stored on user’s local machine. On establishing connection with Exchange Server, every single change made to the user mailbox items gets reflected on Exchange Server simultaneously.

These .OST files may get damaged, corrupt or inaccessible due to numerous unseen reasons such as virus attacks, synchronization problem, network issues, mailbox corruption, oversized OST file, damage of database, breakdown of Exchange Server, software or hardware malfunctioning, insufficient storage space, accidental deletion of Server, abrupt application or Server shutdowns, etc.

In case MS Outlook fails to synchronize .OST files with MS Exchange Server, you might face some error messages. Failure in the synchronization of .OST files with Exchange Server may also lead to missing of files in Outlook mailbox. OST Integrity Checker (Scanost.exe) is an inbuilt utility by Microsoft that assists in checking and repairing the synchronization issues of MS Outlook.

While using OST Integrity Checker tool, MS Outlook mail account must be connected with the Microsoft Exchange Server. It is also to be noted that, while using OST Integrity Checker tool, it does not make any changes to the running MS Exchange mailbox. The tool scans both .OST file and mailbox on the Server running Exchange, compares the items and folders in each and tries to reconcile synchronization differences between them.

An error message that you might face when while synchronizing an .OST file with MS Exchange Server fails:

Unable to start processing services. /offline.ost cannot be accessed. You must connect to your Microsoft Exchange Server computer at least once before you can use your offline folder file.

Steps – How to Repair MS Outlook .OST File using OST Integrity Checker (Scanost.exe):

1. Locate Scanost.exe tool. In case you are using Outlook 2010, it could be found at “C:\Program Files\Microsoft Office\Office14” or in case you are using Outlook 2013, it will be at “C:\Program Files\Microsoft Office\Office15”.
2. Open your Outlook MS Exchange account.
3. Double-click Scanost.exe and click “Browse” to select the .OST file that needs to be repaired. Open “Options” dialog to specify the scan log options and click “Start” to initiate the scanning process. The Scanost.exe tool syncs local .OST content with respect to Exchange mailbox.
4. In order to get the same .OST file fully repaired, it can be rescanned with Scanpst.exe as well. In case, any errors still remains in local .OST file after repairing with Scanost.exe tool, the Scanpst.exe repairs them.
5. On completion of the repairing process, following window appears displaying the folders and items found in the local .OST file:
In case, you are using Microsoft Exchange account and the .OST file is missing email items or is not synchronized with the Exchange mailbox, it is recommended to recreate the .OST file.

Steps – How to Re-create an Offline Outlook Data (.OST) File?

  1. Exit MS Outlook.
  2. In Control Panel > Click Mail.
  3. The title bar of the Mail Setup dialog box displays the name of the current profile. To select a different existing profile > Click Show Profiles > Select the Profile Name > Click Properties.
  4. On the E-mail tab > Select the Exchange Account > Click Change.
  5. Clear the Use Cached Exchange Mode check box > Click More Settings.
  6. On the Advanced tab > Click Offline Folder File Settings.
  7. Click Disable Offline Use > and then in the dialog box that appears > Click Yes.
  8. Again, click Offline Folder File Settings > Click OK > in the dialog box that appears > Click Yes.
  9. Under Cached Exchange Mode Settings > Select the Use Cached Exchange Mode check box > Click OK > Click Next > Click Finish.
  10. In the Account Settings and Mail Setup dialog boxes > Click Close.
In case, OST Integrity Checker tool fails to repair the damaged .OST file or fails to recover the required email item, then user must prefer to use a prominent third-party tool to repair the damaged .OST files.
Numerous third-party tools are available in the market nowadays for recovering user mailbox data from damaged or corrupt .OST files.  OST to PST is one such advanced and powerful email recovery solution that prominently repairs damaged .OST files, recovers user mailbox data with complete accuracy and stores them in .PST files that can be further easily accessed with MS Outlook. Moreover, the software facilitates saving recovered email data in .DBX, .MSG, or .EML file formats. Extending its full support to all available versions of MS Outlook, Microsoft Exchange Server, Outlook Express and compatibility with all Windows OS platforms, the software is also available as a free trial version letting its users evaluate its capabilities before making an actual purchase.