Secure Email Gateways vs Integrated Cloud Email Security. A practical view of modern email protection

Email remains the most consistently exploited attack vector. Phishing, business email compromise and credential harvesting continue to bypass controls, even in organisations with mature security stacks. The reason is simple. Email has evolved. Many legacy protections have not.

For years, the Secure Email Gateway has been the foundation of email security. More recently, Integrated Cloud Email Security has emerged as a complementary approach, particularly for cloud first organisations. Understanding the difference matters when assessing risk and deciding where to invest.

Secure Email Gateways

Secure Email Gateways act as an inline control. Messages are inspected before they reach the mailbox, filtering spam, malware, malicious links and unauthorised content.

Commonly deployed platforms include TrustLayer, Proofpoint, Mimecast in its traditional gateway model, Cisco Email Security and Barracuda.

Strengths

- Proven and reliable. SEGs are mature technologies with a long track record.

- Preventative control. Malicious emails are blocked before a user can interact with them.

- Strong policy control. Effective for spam filtering, attachment inspection and data loss  - prevention.

Well suited to hybrid and on premises environments, including legacy Exchange.

Limitations

- Reduced effectiveness against modern attacks such as social engineering and supplier impersonation.

- Heavy reliance on static rules and signatures, increasing operational overhead.

- Deployment complexity including mail flow changes, MX records and TLS configuration.

- Limited visibility and control once an email has been delivered.

SEGs remain highly effective for known threats and compliance driven controls, but they were not designed to understand context, behaviour or intent.

Integrated Cloud Email Security

Integrated Cloud Email Security takes a different approach. Rather than sitting inline, these solutions connect directly to cloud email platforms using APIs and monitor activity inside the environment.

Examples include Abnormal Security, Egress by KnowBe4, Material Security and Microsoft Defender for Office 365.

Strengths

- Post delivery detection and remediation. Malicious emails can be removed after reaching the inbox.

- Behavioural analysis using machine learning. The focus is on anomalies, relationships and intent rather than signatures.

- Rapid deployment with no changes to mail routing or DNS.

- Strong capability against business email compromise and impersonation attacks.

Limitations

- Reactive by design. There is a short exposure window between delivery and remediation.

- Cloud dependency. Capability is reduced or unavailable in on premises only environments.

- Email centric scope. Additional tools are required to protect collaboration platforms and file sharing.

- Cost considerations when deployed alongside existing gateway controls.

ICES solutions excel at identifying threats that look legitimate on the surface but are malicious in context.

Competing or Complementary

For most organisations, this is no longer an 'either or' decision. The most resilient architectures use layered controls.

A Secure Email Gateway provides baseline hygiene, policy enforcement and preventative filtering. Integrated Cloud Email Security adds behavioural intelligence and visibility inside the mailbox, where many modern attacks succeed.

A useful way to frame this is defence in depth. One control focuses on stopping known threats at the perimeter. The other focuses on detecting and responding to subtle, human focused attacks that evade traditional filtering.

NetUtils perspective

Email security has shifted from purely technical inspection to understanding human behaviour and business context. Static controls alone are no longer sufficient, but they are still valuable.

Organisations that rely solely on a traditional gateway should reassess their exposure to impersonation and business email compromise. Equally, replacing a gateway entirely may remove important preventative and compliance controls.

In most environments, the optimal approach is hybrid. A Secure Email Gateway continues to handle the heavy lifting. Integrated Cloud Email Security provides intelligent oversight within the email platform itself.

The goal is not more tools for the sake of it. The goal is reducing risk in a way that is proportionate, manageable and aligned to how email is actually used today.