OST file is a local data file created by MS Outlook email client for Windows that stores all types of email data like Mailboxes, contacts, calendar, tasks, notes & journals. This file helps the user to access and manage Outlook data in offline mode.

vMail OST to PST file converter (https://filehippo.com/download_vmail-ost-to-pst-converter/) is an email converter software to convert ost to other formats like PST, MSG, MBOX, EML, EMLX, HTML, PDF, RTF, etc and also export local Outlook data to Office 365 or Exchange Server.

This OST conversion software is capable of recover data from corrupt & encrypted OST files and supports the unlimited size of the OST file. This tool is compatible with all the latest versions of Microsoft Outlook software and Windows 10.

More Info- OST to PST Converter (http://eraser.heidi.ie/forum/threads/ost-to-pst-converter-for-microsoft-outlook.14103/)