Users can import OST to Outlook.com, so you have to get the best converter software, eSoftTools OST to PST converter software. This software has multiple file formats such as OST to PST, EML, EMLX, Yahoo Mail, Gmail, MBOX, etc. This software has PST splitting users can split PST files into multiple small sizes. It has a demo version that allows users to convert 25 items from each folder.