I’ve used the repair tool when this started and it did not really repair the file. I used the following combination of techniques to get the user working. In the FixTechGuide support for Office 365 Folder Pane, you might see a folder named Recovered Personal Folders that contains your default Outlook folders or a Lost and Found folder.

Repair Outlook Data Files (.pst and .ost)

If you're using an Exchange email account, you can delete the offline Outlook Data File (.ost) and Outlook will recreate the offline Outlook Data File (.ost) the next time you open Outlook. Even with the reg hack in place, I’ve found that ost files over 50gb tend to corrupt and become unusable with regularity. OST file corruption is a common problem faced by Outlook users like you. While you seek to counter this problem, you look for effective techniques. Although there are many methods to try, a few are productive.

Outlook - OST file recurring corruption

Although the repair process might recreate some of the folders, they may be empty. The disable faulty add-ins in Outlook Lost and Found folder contains any folders and items recovered by the repair tool that Outlook can't place in their original structure. You can use the Inbox Repair tool (SCANPST.EXE) to diagnose and repair errors in your Outlook data file.

• Open the OST file as per the location provided in the table.
• 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.
• 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.
• The file would get inaccessible and won't update in any case.
• We will help our readers decide the best way to rebuild OST for functioning through Outlook.
• 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

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

This article offers to rebuild the OST file without putting you in any difficulty. While this is an effective model, the discussion would revolve around all possibilities. We will help our readers decide the best way to rebuild OST for functioning through Outlook. Office 365 Sync Errors Fix For the past 2 weeks, the OST of my Desktop Outlook has been corrupting continuously. I have 2 computers and both have been facing the same issue.