You can check the location of your Outlook Data description here Files in Outlook.

Repair Outlook Data Files (.pst and .ost)

Click the "Data Files" tab on the window and select your respective OST file. Click the "Open File Location" button to lead to the folder automatically. Outlook OST is directly connected and synchronized to the email client. If the problems occur across the synchronization of the OST file, it would be damaging. The file would get inaccessible and won't update in any case. To the ones that said 50Gb are more than enough for most people,… well we are in 2020 & I can assure you that more than half of the accounts we manage are way above 50Gb, close to 100Gb actually.

Outlook - OST file recurring corruption

The functionality is diverse, and it can be approached in multiple directions. When the case comes to rebuilding the OST file, there are several things to look out for. If Office 365 Sync Errors Fix you can open the original Outlook Data File, you might be able to recover additional items. The Inbox Repair tool creates a backup file with the same name as the original, but with a .bak extension, and saves it in the same folder.

• 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.
• Although the repair process might recreate some of the folders, they may be empty.

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

Fwiw, responding to my original post and how we addressed it for this user - we ended up creating new Outlook profile and limiting the amount of cached mail to 2 years. If the OST still gets corrupted when you have reduced the size there is something in the mailbox causing the problem. You must re-select "Account Settings" when it opens across a drop-down menu. There, lead into the "Data Files" tab and select your OST file. After selecting the file, click on "Open File Location" to redirect to the folder.

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 disable faulty add-ins in Outlook of the location. If you know the location, click on the "Add File" tab and browse it.