As far as I know, the freeware OST to PST Converter software can only convert the first fifty items per folder. To convert unlimited OST files into PST, EML, and MSG format, you need to go with the full version of OST to PST Converter tool. This tool also provides an easy and fast solution to repair corrupted OST files, restore deleted items, and export OST to Office 365 and Live Exchange Server. It also lets the users save OST to PST, Zimbra, Gmail, vCard, ICS, office MSG, EML, EMLX, MBOX, PDF, NSF, and etc. file formats.
This OST to PST exporter tool is the best tool to smoothly export data from OST file to Outlook PST file. You can use this trial version of OST to PST exporter software, this software will help you to export emails from OST to PST file format. This software supports all versions of Windows OS and MS Outlook 2003, 2007, 2010, 2013 and 2016.2019. You can download the free trial version of this software which converts a few items from each folder. You can download this tool from here: -https://www.betavare.com/ost/pst/