What Is the OST File?
Microsoft Outlook normally relies on your Exchange server to show and update your email messages, calendar and other data. However, it’s possible to tell Outlook to back this data up to an offline file, just in case you need access to this information when away from Exchange. The OST file stores a copy of your Outlook folders and automatically syncs with the Exchange service whenever you regain access. It is not necessary to enable offline Outlook use, but Outlook may have trouble running without the OST file.
Access Your Mail Settings
Fixing the missing OST file isn’t done through Outlook, but through the Windows Control Panel. Close Outlook and open the Control Panel by swiping to the bottom right corner of the screen, clicking “Settings” and choosing “Control Panel.” Open the “Mail” option, click the “E-Mail Accounts” tab and choose your Exchange account. Click the “Change” button to gain access to the options available for that account. If you do not have administrator access to your PC, you may not be able to open this menu or modify its settings.
Disable Offline Use
Once inside the “Change” menu, you’ll be able to modify Outlook’s offline settings. Clear the check box next to “Use Cached Exchange Mode.” Next, click the “More Settings” button and select the “Advanced” tab. Choose “Offline Folder File Settings.” Click “Disable Offline Use” and then confirm your choice on the dialog box that appears. This will clear the old OST file and prepare your system for a new one.
Recreate the OST File
Click “Offline File Folder Settings” again. Click “OK” when prompted and confirm your choice by clicking “Yes” in the box that appears. Re-check the box next to “Use Cached Exchange Mode,” click “OK,” select “Next” and click the “Finish” button. Close the “Account Settings” and “Mail Setup” boxes when you’re finished. Outlook will have created a new OST file that can be recognized the next time you open the application.
