A stranger can send email as harbor-legal.example, and nothing stops it.
A forged payment request in the firm’s name could reach its clients’ inboxes.
Observed: p=none asks receiving servers to take no action, so mail forged in the firm’s name is not stopped.
Re-run it from any terminal. So can your insurer.
Switched on in one click where we can reach the firm’s DNS host; where we cannot, the exact record to publish, re-checked until it is closed.