You can check the location of your Outlook Data recreate Outlook profile step by step 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

You surely won't be disappointed with the results of rebuilding OST. As you change the extension, relaunch Outlook Troubleshoot Office 365 Sync and Login Issues to rebuild your OST file. The first solid question that comes to mind is whether OST files are rebuildable. We are aware that OST files are directly connected to the Outlook email.

• When Outlook is running and is halted in such a way, it can damage the OST file.
• Convert your OST to PST for optimal results if rebuilding the OST file does not do the trick.
• The Inbox Repair tool checks the Outlook data files on your computer to see if they're in good shape.
• You can try syncing outlook file 6 to 12 months or through archiving email using retention policy, could be a better way to protect the .ost size from corrupt.
• As you said Outlook E3 licenses should support at least 100GB of data & there’s no excuse why it can’t support OSTs above 50GB when they offer twice that space.
• 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.
• You can use the Inbox Repair tool (SCANPST.EXE) to diagnose and repair errors in your Outlook data file.

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

When Outlook is running and is halted in such a way, it can damage the OST file. You might be working on something important across it when it happens. As you said Outlook E3 licenses should support at least 100GB of data & there’s no excuse why it can’t support OSTs above 50GB when they offer twice that space. In addition, you could open outlook in safe mode, maybe some add-ins affect the outlook. You could Right-click the Start button, and click Run, type Outlook.exe /safe, and click OK. Refer to this blog Solutions To Fix Error – "Errors Have Been Detected In The File Xxx.Ost" Solutions To Fix Error – "Errors Have Been Detected In The File Xxx.Ost" for the solution to this OST error.

Method 4: Use OST Repair Tool

In certain cases, you must go for other methods to recover the data across OST files. If the respective file is not rebuilding from the above methods, there are other ways to get its data. This can be done with the help of PST files, another Outlook data file form. While they act as the basic backup data file for the user, the OST file rebuild Outlook data file quickly can be easily converted to this form. Also, I forgot to mention that normally when the OST is corrupted you normally delete the file and recreate it.