Export mailbox as a PST fileLogin to Outlook with the Exchange account that was used to create the OST files. And to export the OST mailboxes to PST, follow the simple procedure:
Go to Files >Open & Export and click Import & Export.
Select Export to a file; then click Next.
Select the second option—Outlook Data File (.pst)—and click Next.
Select the folder which you want to export and click Next.
Browse the location where you want to save the new PST file and choose the options regarding the duplicate items.
There is an optional choice to provide a password to the PST file, but you can easily move ahead without choosing it.