OST (Offline Storage Table) is like a carbon copy of Exchange Server's mailbox which contains mails, notes, calendar items, contacts, tasks and lots more. The emails, drafts and notes of Microsoft Exchange mailbox are stored in the offline folders as a backup that can be used in case of limited or zero connectivity. There are several reasons of crash and corruptions of these folders due to which they become unreadable like server crash, deletion of user account on MS Office email client and corruption in Exchange database and various other reasons.
Some more error like :
"Unable to open your default email folders. The file abcd.ost is not an offline folder file."
“When folders could not be opened. Errors detected in offline ost file abcd.ost. Exit from all mail-enabled applications, and then use the ost to pst converter tool.”
“Encounter a large numbers of conflict items”
“Unable to open a selected Outlook items when offline.”
“Different type of errors when synchronizing Exchange Server mailbox with your OST file.”
This can be recovered by converting the exchange emails into personal tables. This task of conversion is possible with Manually and with third party OST to PST Conversion software.
Firstly : Converting OST to PST File Manually – Step by Step Guide
Outlook has Import & Export feature which is known to be the ideal way to export mailbox items.
On the top of MS Outlook, click File menu, then “Open” and go to “Import”
When “Import and Export Wizard” is opened, choose “Export to a file”. Then click “Next”.
Choose “Outlook Data File” in the list and click “Next”
Choose mailbox folder to export. You can also add subfolders.
Now you have to define location to save new PST file. Click “Finish” to start process
If you still not able to do this, you can use a third party application like OST to PST Converter tool. There is no technical skill is required to access this application. This tool not only convert ost to pst file as well as recover deleted emails. Go through a Free trial version and use it. Free trial version will show you the preview of converted data. If you feel that tool is working for your then you need to purchase the full version license.
Just click : http://www.osttopstconverter-tool.com/
Regards