How to Recreate an Offline Outlook Data (OST) File in MS Outlook 2010

When you use an Exchange account, your emails and other mailbox items are stored on a mail server. If you want to work offline when Outlook is not connected to Exchange, you can do this by configuring offline mode (or Cached Exchange Mode) in Outlook. The offline working in Outlook is facilitated by OST. In offline or Cached Exchange Mode, Outlook keeps a local copy of emails and other mailbox items as offline Outlook Data File (OST).

Offline Outlook Data File (OST)

While working in the offline mode, the OST files hold the data of the Outlook profile. When Exchange connection is established, OST files are synchronized with the Exchange mailbox to make their data identical. As OST file is a replica of the Exchange mailbox, there is no need to back up OST. When necessary, Outlook can create it from the Exchange mailbox.

Synchronization Errors in Outlook

Sometimes you may find that items are missing or inaccessible in OST file or Exchange mailbox even after synchronization. This is because of errors in the synchronization. In earlier versions of Outlook, Scanost.exe (OST Integrity Check Tool) was available to fix the synchronization issues. However, it is not available in Outlook 2010. But users can re-create the OST file to fix the issue.

OST Corruption

If you are not able to open the OST file, you can presume that it is corrupt. Upon trying to open a corrupt OST, you may receive messages of the type:

• OST file cannot be accessed in Outlook

• Microsoft Exchange Server reported Error

• Unable to expand the folder

• Cannot open the emails folder. ‘The file xxx.ost  is not an offline file’

How Recreate OST File in Outlook 2010

Exit the Outlook application completely, before starting to create a new copy of the OST file.

1. Go to Control Panel and click/double-click Mail.


2. The Mail Setup dialogue box with the name of the current profile appears; click E-mail Accounts….

Note: To change to a different profile, click Show Profiles; select the required profile and click Properties.

3. On the E-mail tab (of the Account Settings dialogue box), select the Exchange account; click Change.


4. Clear the Use Cached Exchange Mode checkbox; click More Settings…


5. Click Offline Folder File Settings on the Advanced tab.


6. Click Disable Offline Use; click Yes in the appearing dialogue box.


7. Again, click Offline Folder File Settings; click OK.


8. Click Yes in the appearing dialogue box.


9. Select the Use Cached Exchange Mode check box under Cached Exchange Mode Settings.


10. Click OK; click Next; finally click Finish.


11. Click Close in the Account Settings and Mail Setup dialog boxes

How to Fix OST Corruption Issues after Exchange Disasters and Crashes

It is not possible to recreate the OST file at a time when Exchange is down due to crash or disaster. But it is possible for you to use the offline files to establish the Outlook communication. For this you need to convert your OST files to PST using a professional tool like Kernel for OST to PST. To know more about this tool visit here: http://www.osttopstconvert.recoveryfiles.org