Cause and Method for Issue OST Synchronization with Exchange Server

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unnamedOST file is regularly synchronized with MS Exchange server and this builds the data in OST file as per the changes done on the server. The changes done in OST file is also synchronized with the Exchange mailbox when network server is connected. But issues with network or some other issues can block the synchronization and cause the OST file throw errors. This section below discusses about the synchronization, associated errors and methods to resolve it.

How Server and OST Synchronization Happens?

MS Outlook synchronizes the OST file folders when users select the Synchronize option available in Tools. Users can also press F9 and synchronize the data directly. A particular folder or all folders together can be synchronized as well. In general, estimation of synchronization process and rate is that a typical 28.8 KBPS dial-up connection will take at least 5 minutes to sync 20-50 emails. This time period also depends on size of email or attachment and also the internet connection speed. MS Outlook version also plays important part in the synchronization as old versions take comparatively more time.

MS Outlook does the synchronization automatically when changes are made with OST file and is connected to server, the changes will synchronize. Previous versions like Outlook 2003 and before, object level of item synchronization occurred. This means that the changes done to any item (at item level) with its property, then the complete item will be synchronized between OST and server. For e.g. if any certain message is forwarded or replied, the changes are synched as per the changes in flag of “relied to” property.

Reasons Behind the Synchronization Issues in OST

In case any issue comes in the synchronization process, OST file shows an error like;
“OST Synchronization Error: 8004011D-526-80040115-0”

The flow of MS Exchange and OST file synchronization can be affected due to various reasons. The most common reasons for synching issues are;

    • Network connectivity issue is the prime reason for synchronization errors.
    • Microsoft Exchange Server downtime can also cause this error.
    • Client machine with configured MS Outlook has some issues with working.
    • Some malicious code running through server or it has been attacked by virus intrusion.
    • OST file structure has been corrupted and thus the error is prompting because of synchronization failure.

All these reasons can lead to the OST file synchronization error “8004011D-526-80040115-0”. This error indicates that the synchronization of OST data file couldn’t happen with MS Exchange server.In such situation, MS Outlook is unable to read the changes and the changes done are not accepted in OST file and vice versa. Visit it-

Error Logs and Method to Resolve It

MS Outlook application comprises of a Sync Issues Folder which comprises the error entries.


The error clearly shows that some network issues have arrived. These logs help to find the root cause of the error. One can also take help from administrator to troubleshoot the problem of MS Exchange server. You can follow the below mentioned steps as an initial actions taken for such errors;

      • Connect the Exchange Server again and check if its connection is done properly or not.
      • Recreate the profile again which is creating problem.
      • If backup is available of OST file then restore the file from the backup. But make sure that the backup has the latest data backed up.
      • Run OST integrity tool to check if any internal damages in OST file is causing this error.


This error can be caused because of the synchronization issues. Exchange server network issues are considered as the prime cause for the sync errors. If following the above steps, error persists to show up; you will have to go for a third party solution like OST Recovery. Such tools are capable to resolve all types of errors in OST file and recover the data in another PST file.

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I am danielle alden, a software developer

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