Do you want to add mass OST file to Outlook? If yes is your answer, then you can use OST Converter software that helps you to convert unlimited OST file to PST file format including all emails, contacts, calendars, etc. without Outlook. It has a very simple GUI, everyone can easily handle and manage the software without technical help. There is no file size limitation, one can migrate a large size of OST file into PST file format without any data loss. It was compatible with all the latest and below versions of MS Outlook and Windows OS including Windows 11.