Why can't I delete the Mail App after installing Mojave?

Hello,

Previously, I have been able to delete/uninstall Os X apps after installing the updates, however this time the OS is claiming that it needs the Mail app to function, "“Mail” can’t be modified or deleted because it’s required by macOS."

I even tried logging in as the root user to delete it, to no avail.

What's the deal here?

Thanks!