How to convert ost to pst without Outlook? Users can easily convert OST to PST without Outlook without losing any important data of OST files. For this, you need to use SysInspire OST to PST Converter software. It will allow users to easily convert OST files to PST without Outlook requirements. It supports all versions of Outlook and is capable of smoothly working with all Windows O/S editions without facing any problems. To check the tool functionality you can try the free demo version of this software, it allows you to convert 25 emails from every folder of OST file.