Is your OST file heavy in size? So use the best third-party tool
Bulk OST to PST Converter application that has an advanced feature for splitting the large file into several small files according to your requirement. With the help of this application, the users see the preview of recovered mailbox along with the Metadata properties like To, Cc, From, Date, Time, Subject, Object and Bcc. No matter what is the size of the file because it easily handles it without creating any difficulty? To preserve the data you can choose one file format from PST, EML, EMLX, HTML, MBOX, vCard, HTML, vCal, MSG these formats as per your need.
Read More info: https://ats-ost-to-pst-converter-toolkit.en.softonic.com/