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 Outlook Login Issues Troubleshooting 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)

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 Outlook synchronizing folders error 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.
• 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.
• 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

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

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 clear Outlook credentials manager 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.