To import an OST file to Outlook, it is necessary initially to convert the OST file to PST. This is because Outlook does not support direct import of OST files. The easiest way to do this is by using a specialised OST to PST conversion tool like Shoviv OST to PST Converter. As a competent OST to PST converter, Shoviv OST to PST Converter is an efficient and easy to use utility that provides a quality conversion mode. It is compatible with all outlook versions and can work with extremely large ost files. It has the ability to maintain folder structure, properties, and layout of your mails, calendars, contacts and other items of the mailbox while migrating the same. After getting the PST file, you can easily relocate the PST file to your Outlook account via the import export option of Outlook. You are guaranteed an easy transfer of your mailbox data to Outlook, this means that you are able to check your emails, calendars, and contacts without any challenges. Read more- https://www.shoviv.com/blog/how-to-import-ost-file-into-outlook-2016-2019-2013/