The most important thing is having your own domain. Then whatever provider you choose, the address is easily portable.
I've no idea what your requirements are, but I've used office 365 small business premimum plan for years (£9.40 per month). It comes with a hosted exchange server which gives you loads of flexibility for very little effort. And for my purposes, I really like outlook as a desktop client. Not everyone agrees though. And as I want the desktop office apps anyway, the extra money for the plan with exchange included is minimal.
There is also a cheaper 'essentials' plan which gives you the server stuff without the desktop office apps if you don't need/want/like them.
I've no idea what your requirements are, but I've used office 365 small business premimum plan for years (£9.40 per month). It comes with a hosted exchange server which gives you loads of flexibility for very little effort. And for my purposes, I really like outlook as a desktop client. Not everyone agrees though. And as I want the desktop office apps anyway, the extra money for the plan with exchange included is minimal.
There is also a cheaper 'essentials' plan which gives you the server stuff without the desktop office apps if you don't need/want/like them.