If someone unsubscribes from an email campaign, they might not know they might still be receiving transactional emails since the unsubscribe does not automatically apply to all communications. Instead of a simple "You are now unsubscribed", maybe have an additional message stating something like "You might still be subscribed to receive transactional emails. Do you want to unsubscribe from all communications with ...? If so, click the button below"

That way, the contact won't receive emails when they expected to have been removed from the list (reducing the risk of spam complaints), and giving them an active role in managing their subscription.