Converting PST files from Outlook to MBOX format can be done easily using a reliable tool like Advik PST to MBOX Converter. Follow these steps:

Download and Install the Software

Download Advik PST to MBOX Converter from the official website and install it on your Windows PC. You can also try the free demo version to test the tool.

1. Add Your PST File: Launch the software and click on “Add PST” to select the Outlook PST file you want to convert.
2. Select MBOX as Output Format: From the list of export options, choose MBOX as the desired format for conversion.
3. Choose Destination Folder: Select a location on your computer where you want the converted MBOX file to be saved.
4. Start the Conversion: Click the Convert button to begin. The software will safely export all your emails, attachments, and folder structure into MBOX format.

https://www.adviksoft.com/pst/mbox.html