What is the need to recreate an OST file?

An OST file is a data file in Outlook that stores a local copy of mailbox items, including emails, contacts, calendars, notes and attachments. It's created when Outlook is set up with an Exchange, Office 365 or IMAP account, enabling you to access your mailbox items even when you are offline. The changes made to the OST file are synchronized with the mail server once the internet connection is restored.

However, various events like system crashes can cause OST files to become damaged, making them inaccessible to Outlook. This results in Outlook synchronization issues and error messages. Although you can recreate or rebuild a new OST file to fix this issue, it may lead to data loss and missing mail items that are not synchronized with the mailbox on the email server.

When your Offline Outlook Data File (OST) becomes corrupt, you will no longer be able to access your mailbox data. Though you can sign in to your live mailbox in a web browser and access your emails from the Outlook Web Application (OWA), you must first recover or rebuild the Outlook OST file if you want to access your local mailbox data offline.

1. How to recreate OST File in Microsoft Outlook 2019, 2016, 2013, 2013 and 2010?

   Although the OST file corruption can be resolved by recreating or rebuilding a new OST file, it frequently results in missing mail items and data loss because the new items may have not synchronized with the email server's mailbox. As a result, rebuilding an OST file while avoiding data loss requires a methodical approach.

   • Method 1: Rebuild an OST file by enabling the Cached Exchange Mode

     The Cached Exchange mode enables an offline copy of the Exchange server’s mailbox on your computer in the form of an OST file. The following steps describe how to enable Cached Exchange Mode in Outlook.

     • Step 1: Open Microsoft Outlook and go to the File menu
       • Click on the ‘File’ menu in the top left corner of the Outlook window.
     • Step 2: Select the Outlook Account Settings
       • From the drop-down menu, select ‘Account Settings’ and then choose ‘Account Settings’> again.
     • Step 3: Enable the Cached Exchange Mode for your email account
       • Select the email account that you want to recreate the OST file for and then click on ‘Change’.
       • In the Change Account window, check the box that says ‘Use Cached Exchange Mode’ and click ‘Next’.
       • Click ‘Finish’ to complete the operation.
     • Step 4: Close and relaunch Outlook to recreate the OST file
       • Outlook will automatically create a new OST file for the email account that you selected in step 4.
   • Method 2: Rebuild an OST file in Outlook 2019, 2016 and 2013

     You can also recreate an OST file by renaming or moving the existing OST file from its location. Before you rename the OST, ensure that you copy and take a backup of the file.

     • Step 1: Close Microsoft Outlook if it is open.
       • Close Outlook and make sure it's not running in the background.
     • Step 2: Navigate to the location of the existing OST file.
       • The default location is usually in the following path:

         C:\Users%username%\AppData\Local\Microsoft\Outlook\

       • You can also locate the OST file by going to File > Info>Account Settings > Account Settings > Data Files > Open File Location.
     • Step 3: Rename the existing OST file
       • Locate the OST file you want to recreate and rename it with a different file extension. For example, change the extension from .ost to .old.

         

     • Step 4: Relaunch Microsoft Outlook to rebuild the OST file
       • A new OST file will be automatically created and start synchronizing with the Exchange server.

       See steps to rebuild an OST file in older versions of Outlook (2013, 2010, 2007 and 2003)

     Limitation: When you rebuild the OST file with this method, any changes saved in the local OST file are completely lost. For instance if you have missing emails that were not synchronized with the Exchange server, you will not be able to recover these mail items. In order to restore any email data or deleted items from the OST file, you must convert the OST to PST.

   • Method 3: Rebuild an OST file with EdbMails OST repair tool

     EdbMails OST to PST converter tool can help you recover and rebuild the OST file from corruption and supports all the OST files from Outlook 2019, 2016, 2013 and Outlook 2010. EdbMails quickly recovers the entire OST file and converts the OST to PST file which is useful to rebuild your corrupt OST file. You can then import the PST file into Microsoft Outlook to restore your mailbox data.

     Steps to rebuild and convert the OST to PST

     • Step 1: Install EdbMails OST to PST software tool
     • Step 2: Select the corrupted OST file that you want to rebuild
     • Step 3: Preview and select the emails and folders for export
     • Step 4: Export the rebuilt OST file to PST.
     • Step 5: Import the PST file into Outlook to restore all mail items.