If you have access to the Exchange mailbox, then you can:
a. Backup of your current .OST file.
b. Remove the current .OST file.
c. Create a new local .OST file by resynchronizing with your Exchange mailbox.
d. After that, you will get a new .OST file containing all the contents of your Exchange mailbox.
However, if you cannot access to your Exchange mailbox, or your original .OST file contains something that does not exist on your Exchange mailbox, then you can use a third party tool called
OST Repair Kit is a compact Outlook OST repair tool download intended for all Outlook users who want to how to repair OST files on their own.
For more information:
http://www.ost.repair/
Also look here:
http://www.filerepairforum.com/forum/microsoft/microsoft-aa/outlook/1351-how-to-open-outlook-ost-file
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Marked as answer by
PeterCurt
17 hours 43 minutes ago