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 fix Outlook after Windows update issues 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

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 modern authentication troubleshooting 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.

• 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.
• 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.
• 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

This article has provided an overview of how you can quickly rebuild an OST file. With the methods and Wondershare Repairit for Email, you can make cohesive use of the available resources. Get your OST rebuilt properly with Outlook Stuck on Synchronizing Folders the help of the available techniques.