I want to suggest you eSoftTools OST to PST Converter software because it provides many types of different features that make it a perfect tool. It's also allowed to recover damaged and corrupted OST files before conversion. It gives you multiple types of different file formats to convert Outlook OST files such as EML, EMLX, HTML, Yahoo, Gmail, Office 365, ICS, MSG, VCF, CSV, and MBOX. Download the free demo version of this tool and get 25 mailbox items from each folder.
Read more- Recover damaged and corrupted OST files
If you want to resolve error OST File Not Synchronizing of outlook, you can try the Sysinspire OST to PST Converter software.This software supports to repair all types of OST files and fix Outlook errors. It smoothly works on very Windows OS editions. It is easy to use for technical and non-technical users. In this software you will also get split feature will will split OST into several small PST files. It can import/convert OST file into PST, EML, EMLX, MSG, HTML, vCard, Office 365 and several more formats & email applications.
Read More:- Resolve Error OST File Not Synchronizing