Sorry if I’ve worded it wrongly

Basically I don’t want to bother setting up a mail server. I want some sorta SaaS such as gmail but with my own domain.

I know of NameCheap’s Private Email but they don’t really support the functionality I seek and need: being able to have 1 account divided into, say, 5 or 10 mailboxes, say 2-3GB of storage for each of them, and have, say, 5 people access the same 1 given mailbox with their own login credentials (which is kinda why mailboxes exist to begin with, because sharing creds is not wise as we know). Also, I need to be able to sync that email solution’s calendar with my google calendar and with my windows account calendar, if this makes sense

Do you guys recommend any in particular?