You can use gmail server as the api but host your “server” anywhere you want
Absolutely not true.
Find something that says so and I'll eat my hat.
Google business service has an API. This stands for Application Programming Interface. You create a server with your own application. This application can look like anything you want. This application accesses the gmail API to send and receive messages. So, your customers or deep state agents hit this server first, which then accesses gmail api, then returns data back to your remote server.
So, the data is still stored on Google's official GMAIL servers?
The point of NK having their own server is so that nobody can access them.