Email Cache while using native mail app in iOS

when configuring email accounts in native mail app for iOS, do you store the mail cache anywhere outside the device for quicker access from the app?

I understand mails will be in my mail server, but I'm wondering if there is a mail cache somewhere in the cloud that the native mail app connects to and then that mail cache talks to my mail server.

Or is it that native app connects directly to my mail server for emails and caches a copy of that in my device based on the number of days I configure. So there is no other mail cache in the cloud?

thanks