Edit: We then need a standard for discoverable DNS settings that providers can publish, together with an endpoint that the domain name provider calls to inform the email provider that it should accept email from person@personaldomain.person and forward it to person@emailprovider.com. Then your domain name provider can discover these, and switching email provider can be done with a click of a button without you having to have any knowledge of DNS. Of course email providers will have little interest in supporting something like this, so this is where regulation would be needed.