All of the cybersecurity programs that we have ever evaluated as part of this series have had one thing in common. None of them ever claimed to be completely, 100% effective in every case. And even if they somehow achieved that goal for a brief snapshot in time, hackers are always advancing their tactics and finding new ways to compromise networks. At some point, a threat is going to get through even the most carefully planned defenses.
With something like email, which is designed to foster communications both within an organization and with the outside world, the certainty of threats slipping though the cracks along with hundreds of other legitimate messages is well known.