I need a solution in which I can migrate Office 365 user's mailboxes from one Office 365 tenant to another Office 365 tenant. I found manual method is complicated & impossible for me, so if any tool available please suggest me.
Yes, manual method is quite complicated & difficult to perform and it will time taking a procedure, but with an automated converter tool, you can easily perform Office 365 mailboxes to Office 365 migration. I have found a tool known as SysTools Office 365 tenant to Office 365 migration tool, it will migrate mailboxes from one Office 365 to another Office 365. You can try this solution it will help you to perform this task.