We provide detailed instructions on how to view your MBOX exports using MBOX Viewer as it is free solution and is fairly simple to use.
To start download and install SysTools mbox viewer https://www.systoolsgroup.com/mbox-viewer.html
Step 1: Extract the zipped up email archive file provided to you
1) Download and Extract the Gmail Export that we have sent you. The archive file is in .ZIP file format.
2) Extract the .zip file that you received. Once extracted, you will have several MBOX files which are each named according to the corresponding label in Gmail. Please note the location of where you extracted the files to.
Step 2: Open Extracted File
1) Next Open MBox Viewer and click Add File and Navigate to your extracted file.
2) once your file is opened you can begin navigating your archive.