- Advance outlook.ost to outlook.pst software is an handy solution which gracefully recover OST file and view OST to PST with mailbox folders- notes, task, contacts, journals, reminders etc. Enstella OST to PST converter application quickly converts OST to PST, EML, MSG and HTML formats. This software has one more brilliant feature that split recovered large PST file into small PST file format during OST to PST conversion process.