In case of accidental file deletion, file corruption or highly damaged ost file, the data cannot be accessed.
So, to make databases accessible, it will become important to import the mailboxes from the ost files.
Follow the steps below to recover the mailboxes for ost File
install SysInspire ost recovery software to open the Outlook ost File, and Install it.
Select the scanning mode to scan the mailboxes from the ost file that you want to be recovered.
Click on the Next button to move in the ost file and then press on the save as the pst options.
After that click on the Next button.
Now, open MS Outlook to explore the ost file and check whether the file is properly restored or not.
More info:- https://www.sysinspire.com/ost-to-pst-converter/