Microsoft OST to PST Converter successfully converts the emails and other contents of the mailbox from offline Exchange OST files to Outlook PST files. It exports all the data from the mailbox like emails, events, calendars, journals, contacts, tasks, etc. Also, it exports the OST files to several other file formats such as PST, MSG, MBOX, EML etc. Using this tool, users can easily migrate from Outlook to other email clients such as Thunderbird, Windows Live Mail, Apple Mail, etc. It restores the corrupt or inaccessible offline data files and exports them to Outlook PST. It does not impose any limitations on file size i.e. users can export the OST files of any size. The software tool widely supports both 32 and 64 bit of Outlook 2016, 2013, 2010, 2007, and other previous versions. Also, it is highly compatible with all the editions of Windows OS. It is available as a demo version so that users can download it for a free evaluation and can purchase the full version later.
Source: https://www.msoutlookhelp.com/ost-to-pst-converter.html