To extract the OST file into MBOX you have to use
SysInspire OST to MBOX converter software. You can convert multiple OST files to MBOX in a single process. In this software, you can convert and store multiple OST files in a single MBOX file. Without the installation of MS Outlook, you can use this software. In the preview panel, you can view the files and folders of the OST file and choose the files and folders of the OST file to convert to an MBOX file. It supports the OST file of Outlook 2021, 2019, 2016, 2013, 2010, 2007, etc. It can work with all editions of the Windows Operating System such as Windows 11, 10, 8, 7, Vista, XP and older versions.
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Extract the OST file into MBOX