Using Outlook PST Converter Tool is considered the most reliable tool to convert PST files to MBOX format. It easily converts multiple PST files to MBOX format while maintaining the original folder structure. The tool converts PST files to MBOX, PDF, EML, MSG, TGZ, HTML, and NSF formats—the tool imports PST files for Thunderbird, Gmail, Office 365, Yahoo, etc. Download a free demo version of the tool and check out its functionality and performance.