How to Fix OST File Synchronization Error?

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OST File is created in Microsoft Outlook when Microsoft Exchange account is created. Also known as Offline Storage Table, this file enables users to work when Outlook is not connected to the server. Once the connection is available, you can synchronize all the work in MS Outlook offline with Exchange Server. Indeed, it makes Exchange mailbox in the form of OST file.

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Why OST File Synchronization Error Occurs?

More often than not, you may encounter several synchronization errors when connecting OST to Exchange mailbox. There are different reasons why synchronization is stopped with Exchange in Outlook 2003, 2007, 2010, 2013, 2016 and 2019.

  • Network connection – The main cause of synchronization issue
  • MS Exchange Server also goes down more often due to which Outlook cannot synchronize
  • Problems in local machine are another common issue when Outlook is malfunctioning
  • Sudden system shutdown, large OST file size, and virus attack are some of the common reasons

How to Fix OST Synchronization Issue?

There are different steps you can take to resolve the OST synchronization problem, such as verifying user profile, cached exchange mode etc. Here are some of the important steps to get rid of this problem –

Step 1 – Verify Synchronization of OST files

Consider the following steps to check synchronization of Offline Storage files in proper way –

  • Right Click on the folder you want to check and click “Properties”
  • Switch to “Synchronization” tab
  • Select “Statistics” of this folder and check these attributes –
    • Server folder contains – Items
    • Last synchronized on – Date
    • Offline folder contains – items

If you don’t have any OST File Sync problem, attribute value of the folder of Server as well as offline folder contents are the same. If you couldn’t find these value same, there must be a conflict in syncing both databases. In that case, you have to follow these processes to verify profile settings.

In Outlook 2007

  • Click on “Tools” then “Account Settings”
  • Click “Data File” and set “Mailbox account name as default”
  • In Email tab, go to “Mailbox – account name” and Settings.
  • Check the option “Use cached Exchange Mode” and click OK.

Step 2 – OST File Synchronization

You have to do two important things to sync offline folders – Automatic and Manual, to fix OST file synchronization issues.

For Manual Synchronization

  • Go to “Folder List” pane, choose “Folder should be synchronized”
  • Go to “Tools” menu, click “Send/Receive”, then Microsoft Exchange Server, if you have specific folder
  • In Tools menu, go to “Send/Receive All” for all folders

For Automatic Synchronization

With this method, you can sync OST file with Exchange Server all the time when you go online.

  • Choose “Tools” and “Options”
  • In Mail Setup, select “Send Immediately when connected”
  • In Send/Receive, select “Send/Receive groups” and check “Perform automatic send/receive when exiting”.


Step 3 – Create New OST File and Synchronize

If the above methods cannot fix the OST file synchronization issue and you are not getting it synced, there are chances that OST file is corrupt or damaged. In that case, you have to recreate and resynchronize the OST file.

How to Rebuild New OST?

  • Type *.ost in search box to look for OST file
  • Rename the old file with different extension. For example, replace .OST with .OLD extension.
  • After renaming the file, a new file will be created
  • In Outlook, go to “Tools” and “Send/Receive”

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If the OST file is oversized and is not accessible, an OST Splitter tool can split the file into smaller parts. If you still cannot resolve the OST synchronization issue, you may try scanost.exe or scanpst.exe tools from Microsoft. These are the default repair tools to fix OST/PST file issues. You may try these tools to fix them. If these tools can’t work and you cannot access the OST file data, then use Regain OST to PST Converter to import and access the OST file through Outlook.

Regain OST to PST Converter tool is very reliable and professional as it can easily repair OST files that are severely corrupt or damaged and cannot be fixed by default repair tools. If the above methods are not longer helpful, use this tool to resolve data file problems and recover them with few easy steps.

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