Migration to Office 365:
Moving from Office 365 to Office 365 requires quite an amount of planning and a solid understanding of the email system you are operating. The environment you are in will determine what type of migration you need, such as cutover—staged transition or hybrid. Microsoft offers useful Office 365 migration tools that can assist with every step of the process. To decide what kind of migration to opt for, you can use the Exchange Server Deployment Assistant. It can provide you with alternatives to migrate based on your current settings and the Exchange Server version.
Official website: shoviv.com
IT experts always recommend that you've got the inventory of every asset you own before beginning an upgrade. Being aware of what you have (sites and collections of sites and listed libraries and the size of the database) will be beneficial during the process of migration.
Email softwares from shoviv:-