The Microsoft 365 E5 Security Stack Explained

Published 29/10/25 under:

Microsoft 365 E5 is one of the most comprehensive security suites available, yet most organisations only use a fraction of what they’re paying for.

In almost every review we run, we find the same pattern: E5 licences are deployed, but the security tools that come with them aren’t. Third-party solutions remain in place, configurations are incomplete, and the real value of Microsoft’s integrated security ecosystem never gets unlocked.

The problem isn’t technology. It’s awareness, configuration, and ownership.

This guide breaks down what’s actually inside the E5 security stack, how the components fit together, and how you can start getting the value you’ve already paid for.

The Layers of Microsoft’s Security Model

Microsoft’s approach to security is built around five layers:

1. Identity
2. Devices
3. Applications
4. Data
5. Visibility

Each layer is interconnected, sharing threat signals across the ecosystem to enable detection and response that’s both faster and smarter. Let me delve a bit deeper into each layer…

Identity: Microsoft Entra ID Premium (formerly Azure AD P2)

Identity is at the heart of the E5 model. Entra ID Premium delivers advanced Conditional Access, multifactor authentication, identity protection, and privileged access management.
It allows you to control who can access what, from where, and on which device, automatically adjusting risk levels based on behaviour.

Devices: Microsoft Defender for Endpoint + Intune

Defender for Endpoint provides endpoint detection and response, while Intune delivers centralised policy and compliance management. Together they secure and manage every device connecting to your environment. Real-time telemetry from Defender feeds back into Microsoft’s cloud to improve protection for all customers.

Applications: Microsoft Defender for Office 365

E5 includes full protection across Exchange, Teams, SharePoint, and OneDrive. Defender for Office 365 blocks phishing, malware and business email compromise before it ever hits a user’s inbox. It also integrates with Entra ID to enforce safe links and attachments policies automatically, ensuring the same level of protection across every collaboration tool.

Cloud Apps & Data: Defender for Cloud Apps

This is Microsoft’s cloud access security broker (CASB). Your visibility layer for all cloud activity. It identifies shadow IT, monitors data sharing, and enforces governance policies. Linked with Conditional Access, it lets you block risky apps or limit actions (like downloads) when connecting from unmanaged devices.

Visibility: Microsoft Sentinel

Sentinel is Microsoft’s cloud-native SIEM and SOAR solution. It brings together data from all the above tools, and from third-party sources, into one analytics engine. It uses AI and machine learning to correlate incidents, detect anomalies, and automate response playbooks. For organisations leveraging a Managed SOC, Sentinel provides the backbone for 24/7 monitoring and automated threat response.

Why So Many Organisations Underuse E5

Even with all this capability, many organisations still rely on separate tools. We see the same reasons consistently pop up:

• Teams don’t always know what’s included in their E5 licences
• Configuring each product properly takes effort, and most IT teams are stretched thin
• Existing contracts or “we’ve always used X” thinking makes it hard to remove older tools
• Security teams often trust specialist vendors more than the vendor that also runs their productivity suite
• Microsoft isn’t a major security player?!

But the reality is that Microsoft has invested billions into security, and now operates one of the largest threat intelligence networks in the world. When correctly deployed, the E5 stack delivers end-to-end protection with fewer moving parts and deeper integration.

The E5 Pricing Equation

It’s worth remembering that E5 is more than a security licence. It also includes Microsoft’s full collaboration and compliance suite.

At list price, Microsoft 365 E5 is around £50 per user per month, compared to roughly £33 for E3. That extra £17 often looks expensive at first glance… until you start to quantify what it replaces.

When you factor in the cost of:

• Endpoint protection
• SIEM or SOC tooling
• Cloud app security
• Identity governance
• Email protection and phishing simulation

Most organisations quickly find that E5 delivers stronger coverage at a lower total cost of ownership.

The Power of Integration

Each product in E5 is strong on its own, but the real value comes from how they connect. Let’s talk through a simple, yet powerful scenario:

• A phishing attempt detected by Defender for Office 365 can trigger an automated investigation in Defender for Endpoint if a user clicks a malicious link.
• Conditional Access policies in Entra ID can block that user until the device is remediated.
• Sentinel then logs and correlates the event, enriching it with global threat intelligence and alerting your SOC team in real time.

This cross-signal architecture is what makes the Microsoft security stack unique. It’s not a collection of point tools, it’s a connected ecosystem that can respond automatically.

Making Microsft 365 E5 Work For You

To make E5 work, you need more than licences. You need operational alignment.

That means:

• Designing policies and baselines aligned with your organisation’s risk appetite.
• Integrating threat detection and response into a central SOC platform.
• Regularly reviewing telemetry and alerts to fine-tune controls.
• Replacing legacy systems only once new capabilities are proven in production.

Many mid-market teams don’t have the bandwidth to manage this in-house. That’s where a specialist Microsoft partner with a Managed Security Service becomes invaluable.

A managed partner can deploy, monitor and optimise the E5 stack, integrating Microsoft Defender, Sentinel and Entra into a 24/7 SOC service that provides continuous visibility, response and improvement.

At Kerv, we map your current toolset against E5’s native capabilities, assess configuration gaps, and create a roadmap to unlock the value you already own. In many cases, that process highlights overlapping tools, unmonitored alerts, and opportunities to simplify operations without compromising protection.

Get in touch today!