Online OST to PST file conversion service This online converter of OST files to PST files makes it possible to transfer data from one format to another using any device and any operating system (Windows, Android, iOS, Mac OS, etc). Our OST to PST online conversion service does not require access to Exchange Server, Windows Domain Controller or Microsoft Outlook. All you need to do is upload your OST file to the server. Next, you will receive a link to download the converted PST file containing all of the data from the original OST file, including: e-mails, contacts, appointments, reminders, tasks, notes, calendars, journals, attachments, etc.