Ok, you will have to set the auth.challenge.email.from config setting to a valid email address if your host is localhost
If this is not set, Kirby auto-creates a from address like this:
'from' => $kirby->option('auth.challenge.email.from', 'noreply@' . $kirby->url('index', true)->host()),
which results in the invalid email address if you are not using a proper host address.