There will be times when you cannot open your Outlook Data file, or you can have a suspected Offline Folder file (.ost) t or Personal Folders (.pst) which cannot be opened due to corruption. This article explains how to repair .ost file.
This type of timely error message while synchronizing Offline Folder file (.ost) I Microsoft Office Outlook with your mailbox on a server running Exchange indicates corruptions. You mayalso notice some .ost file item missing from your mailbox after you attempt for synchronization. For Outlook 2010 and previous versions you should use the OST Integrity Check tool (Scanost.exe) which is on of the way to resolve the issue.
The OST Integrity Check tool is provided only for .ost file and can diagnose synchronized corrupt .ost file.
OST file repair tool initiate scan on both your .ost file and your mailbox on the server to compare the items and folders in each, and attempts to reconcile synchronization differences. The tool doesn’t make any changes in the mailbox items running on the online server. The tool records the differences between the .ost file and the mailbox and provides comprehensive report, so that you can check out or any discrepancies. The tool also takes account of any situation that tool cannot resolve and which you will need to fix manually
You will need to connect to your Exchange account so that the tool can scan your mailbox folders and items. If you previously set up Outlook to start offline automatically, the OST Integrity Check tool will not able to access the .ost file. Therefore before you run the tool, you need to change your Outlook startup settings.
For PST files which are not opening you can run Inbox Repair tool (Scanpst.exe) to diagnose and repair the errors in the .pst file. This tool scans the .pst file and make sure that the structure is intact. It does not interact with your Inbox on the server running Exchange server in any way.
Note: The Outlook OST Integrity Checker tool (Scanost.exe) is not installed with Microsoft Outlook 2010 and later versions.
However, now Microsoft recommends deleting the offline Outlook Data File (.ost) and letting Outlook update the information from the server that is running in Microsoft Exchange.
For data that is not present in the Outlook Data server, you can export the data to an Outlook Data File (.pst) a then you delete your offline Outlook Data File (.ost). After the data is downloaded from the server, you can import them back to a new OST file. Do not forget to exclude the duplicate data from the PST file during import.
Well for newest Microsoft Outlook versions this trick may not work as you can read above, there is no utility to repair OST file. You can employ third party software to fix the corrupted ost file.