Searching on the web, I found this informative post and thinking about my contribution as well.

Here I am going to share an article post that will help you all to know step by step Office 365 Migration Guide.

Read here: Office 365 Migration Guide

After reading this article post, you will know the best way to migrate Office 365 mailboxes into Office 365, Live Exchange Server, PST, EML, and MSG. One can also download a demo version to know step by step process of Office 365 Migration.