I would suggest you to use the InQuit OST to PST Converter because with this converter you can split your large OST file into several small PST files as per your need. The size of the OST file does not matter for the conversion process of OST to PST. The user converts their OST data into PST and other formats like MSG, EML, vCal, vCard, MBOX and HTML in the absence of MS Outlook installation.