I favor the most suitable one that is the OST to Office 365 migration tool.
You can also try this OST to Office 365 software and then select a reliable tool.
By helping this OST to Office 365 converter software to migrate OST items into Office 365 account +15 file formats such as- pst, vCard, vCal, Gmail, live Exchange sever, zimbra, MBOX, EML, EMLX, NSF, HTML, PDF, OLM, and etc.http://www.osttopst-converter.com/blog/best-method-to-import-ost-to-office-365.html