So the best converter that can import an OST file in Outlook Office 365 is the SysInspire OST to PST Converter tool. This software is the best to convert my OST file in different formats without any error and safely and the formats are Gmail, HTML, Office 365, EMLX, Yahoo Mail, VCF, CSV, EML, Zimbra Desktop, IMAP Account and many more. The interface of this software is easily understandable and usable. You can work on it without any knowledge of technical things.