If you are aware of "Converting PST to MBOX Format," I'd want to suggest a website You should try to find out where you can learn the best way to do so eSoftTools PST to MBOX Converter Software. It works with a very simple and clean graphical interface to make smooth PST to MBOX file Conversion. Both are accepted ANSI and UNICODE PST files for conversion. Both new and old versions of Microsoft Outlook are supported by the program. All customers of PST to MBOX Converter can use the free demo to easily move up to 25 emails from each folder without having to pay anything.
About us:- Convert PST to MBOX

PST to MBOX convert manually:
Step 1: Open Microsoft Outlook.
Step 2: Go to File and click on Open & Export.
Step 3: Click the Import/Export button.
Step 4: Select Export to a file and click Next.
Step 5: Click on Personal Folder File(.pst) and then click on Next.
Step 6: Now in the Export Personal Folders, check if Include subfolders are selected. Hence all the file will be exported.
Step 7: Save the exported file and click on Finish.
Hope This Helps,
Peter