A few months ago, I got a call that no CIO wants to receive: “We think someone clicked on something they should not have.” It was the familiar moment of dreading the split second where you mentally trace every control you have ever put in place and hope it was enough.

But was it enough?

Even with the magic quadrant top-tier email security services in place, something had slipped through – we know it as a well-crafted phishing email that looked like a perfectly normal internal finance request.

No red flags. No typos. No fancy file extensions.

Just one wrong click.

It is a daily reminder to all and one that I always carry with me: Email security does not end in the inbox. That is just the start.

The Myth of “Before Delivery” Protection

As CIOs, we prioritize perimeter defense. We invest in threat intelligence, filtering layers, sandboxing, and AI-driven anomaly detection. And that is all necessary. It is what keeps the obvious junk out, the 90% of attacks that are generic, automated, and noisy.

But it is the last 10% that worries me the most.

The emails that bypass detection because they do not look malicious. The ones that rely not on malware, but on manipulation.

These attacks do not try to outsmart the machines; they outsmart humans.

And unfortunately, even the best pre-delivery tools cannot protect against that final, fateful decision: the dreaded click.

Post-Delivery: The Missing Layer

We often assume that once an email lands in the inbox, the battle is over. But that’s where real vulnerability begins. Think about it: your users are staring at a message that appears safe. Engagement causes damage regardless of filters.

That is why we invested a few years ago in the post-delivery layer.

Here is what that looks like in practice:

• Real-time analysis inside the inbox. Not just at the gateway. We use a tool that scans delivered messages and removes new threats as indicators evolve. These indicators number in the thousands.

• Dynamic threat retraction. We can retract malicious messages from inboxes before users see them.

• User behavior monitoring. We are paying closer attention to how people interact with emails. Who clicked, what was clicked, and any lateral movement.

Training Is Not Enough, But It’s Still Critical

I used to believe we could “train and retrain” the phishing problem. While education is still critical, we cannot place the entire burden of threat detection on our employees.

Expecting a busy accountant on a busy day, everyone knows what day that is, to spot the difference between a legitimate invoice and a spoofed one, especially under time pressure, is unrealistic.

So, we do both.

Yes, we run simulations twice monthly and one training campaign monthly. But more importantly, we have built resilience into the system. Accidentally clicking an email limits damage and allows a quick response by our support staff.

A Personal Takeaway

The phishing attempt did not lead to monetary loss or data theft, because we caught it early. But it was too close for comfort.

It reminded me that security is never “set and forget.”

It is active. Evolving. And deeply human.

So, if you are a CIO reading this, here is my challenge: take a hard look at your inbox strategy. Are you stopping threats before they arrive and after they have landed? Are you giving your users a safety net, or just hoping they will not fall?

It is not just about keeping the bad guys out. It is about being ready when they are already in.