You can check the location of your Outlook Data Fix Outlook Not Opening After Windows Update Files in Outlook.

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

"Excellent program. Ive used it twice to convert .EML files to .MSG. Thank you." online Outlook email repair utility If anyone can get an answer from microsoft on this issue I’d appreciate it. Any MS techs can contact me if they need further information or analysis. I’ve created a ticket today with Rackspace to see if their other customers are having this issue but I’m not hopeful on hearing back from them.

• 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.
• 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.
• 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 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 solve Office 365 mailbox sync delays the help of the available techniques.