The Aryson OST to PST Converter is a popular tool for converting multiple OST files to PST format at once. This flexible tool lets you save OST files in different formats like MBOX, PST, MSG, EML, EMLX, CSV, and more. It also has an easy and automated process, making it simple to move OST files to platforms like Google Workspace, Office 365, IMAP servers, and others.

Follow these steps to save an OST file as a MBOX file:

1. Download and open the Outlook OST to PST Converter.
2. Click "Select Folder" or "Select File" to add the OST file to the tool.
3. Preview and choose the OST mailbox items from the folder list.
4. Click "File Formats" and select "MBOX" as the format to save.
5. Optionally, choose any extra features or filters from the software.
6. Finally, click the "Convert" button to start the conversion process.