You can check the location of your Outlook Data Microsoft Outlook Email Repair Tool Online Files in Outlook.

Repair Outlook Data Files (.pst and .ost)

This is all most people will need, searching for older items will be slower but for daily use items it will still be quick. As you close them, lead to the folder and right-click on the OST file. Once you re-open Outlook, your OST file is automatically recreated or rebuilt. If your hard drive goes through any physical damage, it will damage the data across it too. A bad sector or corrupted hard drive can cause OST inaccessibility.

Outlook - OST file recurring corruption

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• If you know the location, click on the "Add File" tab and browse it.
• If your hard drive goes through any physical damage, it will damage the data across it too.
• When the case comes to rebuilding the OST file, there are several things to look out for.
• Upon starting Outlook, error message displayed is "Errors have been detected in the file ," then prompt appears to locate (not fix) the OST file.
• Find the .ost file that the error message reported to have errors, and then delete it and open outlook, it will recreate a new .ost file.
• The WebbyAcad OST Recovery Tool offers advanced features to fix damaged OST files and convert them to PST, EML, MSG and other formats while preserving folder hierarchy and metadata.
• Although the repair process might recreate some of the folders, they may be empty.
• Find solutions to common problems or get help from a support agent.

What are the major Reasons of OST Corruption and how to Fix it

Confirmed user can log on to OWA (Office 365 webmail) without issue. Upon starting Outlook, error message displayed is "Errors have been detected in the file ," then prompt appears to locate (not fix) the OST file. Outlook 2016 connecting to Office 365 E3, mailbox size ~55GB and Outlook reghack effected to allow for ~80GB OST. If your computer faces unnecessary power outages during a process, it can be damaging.

Method 4: Use OST Repair Tool

Only way to restore Outlook 2016 (Windows) functionality was to create a new profile; this worked, and a new OST file was created. On the next screen, access the "Find File" option if you are unaware Outlook data file cannot be accessed of the location. If you know the location, click on the "Add File" tab and browse it.