Migrating your email data from an IMAP server to Office 365 can be done using the Exchange Admin Center (EAC), which is a web-based management console for Exchange Online.
Here are the steps to migrate your email data using the new EAC:
Log in to the Office 365 portal with an administrator account.
Go to the Exchange Admin Center by clicking the Admin icon and selecting Exchange from the list of admin centers.
In the Exchange Admin Center, click on the Migration tab, and then click the New (+) button to start a new migration batch.
Select the IMAP migration option, and then provide the necessary details for your IMAP server, including the server name, port number, and admin credentials.
Provide the necessary details for your Office 365 environment, including the target mailbox, and the admin credentials for Office 365.
Select the options for your migration batch, such as whether to migrate all items or only items from a specific date range.
Start the migration batch by clicking the Start button.
The migration process can take some time depending on the size of your mailbox and the amount of data being migrated. You can monitor the progress of your migration batch by going to the Migration tab in the EAC and checking the status of your batch.
Once the Microsoft 365 Migration is complete, you should be able to access your email data in Office 365. It’s recommended that you perform a thorough check of your email data to ensure that all items have been successfully migrated.