You can migrate mail from one Office 365 account to another easily. You can go for the manual method or the professional method.  But the manual method has some limitations that's why the professional method is recommended. Follow the below steps:

Step 1. Download and set Source and Destination platforms.

Step 2. Select the items under the workload.

Step 3. Complete and validate Source and Destination credentials.

Step 4. Load the users and start the migration.