Fix & Repair Synchronization Issues of OST File with Exchange Server

Posted 5, Feb 2019 | By Editorial Team

Exchange mailboxes synchronization with offline counterparts is important for ensuring trouble-free offline working in Exchange interface. However, many users of MS Outlook faces error messages when OST file synchronization fail. Here, in the following blog, we will discuss common synchronization issues of OST and related solutions.

How synchronization works between OST and Exchange Server?

Outlook email application OST file gets synchronized with Exchange Server mailbox only when connected with Exchange. And the synchronization speed varies as per Outlook versions depending on the size of data.

Reasons of OST Synchronization Issues

Synchronization between Exchange Server and Outlook in most situations are smooth. But at times, due to some hardware defects or bad network connection, synchronization can wholly or partially fail. Failure issue of Exchange OST synchronization arises due to damage or OST file corruption.

How Exchange OST Synchronization Error Occurs?

Synchronization errors of OST disturbs lot of Outlook users in multiple ways:

  • Sudden error appears during Exchange synchronization:

“Unable to start MS Outlook. Unable to open Outlook window. Folders cannot be opened. The file abc.ost is not Outlook data file (.ost).

  • Facing Outlook issues when Cached Exchange Mode is enabled and no issues when it is disabled.
  • Mailbox items such as emails, contacts etc. are missing after OST file synchronization with Exchange Server. Facing mismatch of items when retrieving the same mailbox in Outlook and Outlook Web App.

List of Outlook Editions Affected by OST Synchronization issues

All Outlook versions are affected by the synchronization of OST file with Exchange Server such as Outlook 2019, 2016, 2013, 2010, 2007 and 2003.

Solution to Resolve OST Synchronization Error

OST Integrity Check Tool                                 

OST Integrity Check Tool (Scanost.exe) is used with Outlook 2003 and Outlook 2007 editions. If you try to use this tool on recent Outlook editions, then it will not be useful and we are not discussing this in detail.

Manual Offline Folder Synchronization (for Outlook 2010, 2013, 2016 & 2019)

The process will be helpful in fixing synchronization issues at folder level. When you are facing synchronization error with a particular folder, follow this process:

  1. Go to location of OST folder, right-click on it, select Properties.
  2. Click Clear Offline Items and hit OK.
  3. Select Send/Receive tab and click Update Folder.
  4. Make use of Inbox Repair Tool (scanpst.exe – scan and repair damaged OST file).
  5. Rebuild OST file. If you are facing OST issues continuously, rename affected OST and let Exchange create new OST file again.

How to Recreate Offline Outlook Folder Data File (.ost)?

For creating new OST file, follow:

Step 1. Shut Outlook email app.

Step 2. Navigate to C:\Users\administrator\AppData\Local\Microsoft Outlook

Step 3. Find the required OST file and rename the same.

Step 4. Again start Outlook application and wait till mailbox synchronization.

But with this process, you will see that resultant file is lacking in some information or its formatting was altered. In such a case it would be better to go for trusted and secure email conversion application that guarantees 100% accuracy in the outcome. And OST Converter is a solution which is used by many users for converting OST to Office 365. Apart from this, users can move OST files to PST, PDF, MSG, EML, EMLx, MBOX, NSF, Zimbra etc.