A domain subscription checker (done with similar verification to the domain verification links) would enable the domain owner to check only current employees have have access to the information, and to revoke any incorrectly or outdated subscriptions on the domain without having to have access to each destination mailbox

From personal mistake:
I've subscribed for domain alerts, copied the verification token and authorised before it took me back to a screen that showed I'd mis-spelt the notification email address hostname! That means someone else now is approved to see full domain level summary.

As the notification email address is different to the email (webmaster@) that is used to verify...It is possible to setup an incorrect email subscription that cannot be cancelled. by the site owner.