For years, email security has centred around one core goal: stopping threats from getting in.
And for good reason. Inbound attacks — phishing, malware, impersonation — are loud, costly, and immediate. They demand clear defences. They justify investment.
But look at the breach reports, the ICO filings, the quiet regulatory fines. A different story emerges.
The email threats doing the most reputational damage aren’t the ones hammering your perimeter. They’re the ones quietly slipping out.
This isn’t a conversation about missing tech.
Most businesses have access to some form of outbound email control — whether it’s basic DLP rules in Microsoft 365, a feature baked into a secure email gateway, or policies tied to role-based access.
But in reality?
The result is a strange paradox: organisations believe they’re protected, but can’t explain how that protection actually works in practice.
A director accidentally sends a confidential attachment to an external contact with the same first name.
A junior employee replies to a payroll query and includes the wrong department list.
A leaver forwards pipeline data to a personal address two days before handing in notice.
These scenarios don’t trigger alarms. They don’t match a signature or trip an inbound filter. And often, they don’t even get noticed until legal or compliance teams are cleaning up the aftermath.
But they’re not edge cases. They’re common — and increasingly, they’re costly.
According to UK ICO data, misdirected emails accounted for more reported breaches in 2023 than malware, ransomware and phishing combined. The same is true across several industries in Europe and North America.
The cause? Not just human error — but a failure to create an environment where mistakes are caught before they become consequences.
There’s a pattern to underperforming outbound controls. Most fall into one or more of these traps:
Pop-ups that appear too often. Quarantines that delay critical communications. False positives that undermine user trust.
No centralised log of outbound activity. No easy way to trace what data left the business, when, and under whose credentials.
We assume encryption means safe. We assume MFA stops insider risk. We assume people know better.
Those assumptions aren’t malicious, but they’re not protective either.
When outbound controls are configured and delivered the right way, they don’t just prevent mistakes — they create assurance. For IT. For compliance. For leadership.
Here’s what best practice looks like:
The market is full of vendors promising AI-powered phishing detection, zero-day sandboxing, and advanced impersonation filters. And those capabilities matter.
But if your email security ends at the inbox, it’s incomplete.
Email security in 2025 is about lifecycle protection:
Outbound protection is part of that. Not an optional add-on. Not a compliance chore. A core layer of risk mitigation in a world where most data loss is unintentional, internal — and preventable.
If you’re investing in better email security but haven’t revisited your outbound controls in the past 12 months — you’re only telling half the story.
And if your outbound policies exist only in documentation but not in behaviour, the question becomes:
If you’re investing in better email security but haven’t revisited your outbound controls in the past 12 months — you’re only telling half the story.
And if your outbound policies exist only in documentation but not in behaviour, the question becomes:
What’s already slipped through the cracks — and how would you know?
I recently switched to TrustLayer for our cloud security needs, and it's been a great decision. The intuitive interface and excellent support make managing our email platform for over 800 users feel effortless. TrustLayer's emphasis on complete visibility and data protection gives me peace of mind, knowing our business operates fearlessly.
