To add a PST file to Office 365 Outlook, you can use Aryson PST Converter, which provides an easy and efficient way to import PST data into Office 365. This tool ensures smooth migration while maintaining the original folder hierarchy, email properties, and attachments. It allows you to convert PST files into multiple formats like MBOX, EML, MSG, PDF, and HTML, making it compatible with various email clients, including Thunderbird, Gmail, and Yahoo. With its advanced features and user-friendly interface, it simplifies the process of moving your PST data to Office 365 without any data loss or corruption.