To open Offline Folder Files in Outlook you can use OST Recovery Tool. This tool first allows recovery of damaged OST items like emails, messages, contacts, calendars, appointments, etc. and also lets user save them in some different file format such as in PST, MBOX, EML, DBX, etc. Read more visit: http://recoveryandmanagement.com/repair-ost-and-convert-into-pst-outlook/