I want to host my domain in your system and I will need to use 5 premium users 

All the rest of my staff are using my domain email with their own gmail account so its only an Alias user (?! i am not sure)

I have 200 users like this 

I need all my staff to send and receive email from our domain 

what package I will need ?

do I need to pay users for all my staff ?

I am currently on shared email hosting and I have unlimited accounts and space

Thank you