PST to Gmail Migration tool
I would like to suggest the third party tool like the KDETools software PST to Gmail Converter which converts PST to Gmail file format. This software has excellent functions. It can convert PST files to Gmail format with just a few clicks. In addition, it supports conversion to various file formats such as EML, EMLX, Zimbra, MSG, HTML, etc. etc. This tool can import MBOX files into the Office 365 and Live Exchange server.
Click here: https://www.kdetools.com/pst/gmail/