There are various tools available online to convert OST to PST. However, it is hard to say which one is best. Based on my recent experience, I would suggest using Aryson OST to PST Converter tool that converts OST files with ease. It gives multiple saving options like PST, MBOX, MSG, Office 365, Yahoo, Gmail, Hotmail, Thunderbird, etc. Users can transfer all data of OST files such as emails, contacts, calendars, tasks, notes, journals, etc. It is compatible with all Windows versions including the latest Windows 11.