In case you want to migrate your IMAP mailbox to Office 365 admin center then you should go through this informative article that will help you to migrate IMAP to Office 365 using a new exchange admin center. This article precisely explains the detailed manual process.
However, the manual process requires some basic Office 365 admin center knowledge. Therefore, it becomes pretty complicated for non-technical users. For them, this article also introduced one of the best IMAP Backup Tool that ensures high data security throughout the migration process. Additionally, it has a simple and self-explanatory user interface that allows them to perform the whole task quite conveniently.