There are two methods that you can use to repair Outlook PST file if your Outlook PST get inaccessible. First, Inbox Repair tool, the free ScanPST tool provided by Microsoft, i.e. built-in repair tool. Another tool is paid tool that can repair mailbox data from damaged PST files. The choice is Yours!!

For more information about free tool : http://pstrepairtool.blogspot.com/2015/12/most-suitable-way-to-fix-pst-file.html