Gregory's Server@severak did you read the linked article? It covers your second point throughly.
As for the first point, there was a time almost all email was "self hosted". Every business that had a server had a mail server (unless they were a Microsoft only shop). Then Hotmail and then Google started the change.
@aral @cancel
@chromatic @severak @aral @cancel even Microsoft shops. I had many customers for many years who ran local SBS on site mail servers. But using your own onsite MS infrastructure is no guarantee now of reliable delivery.