What Microsoft’s Latest Email Benchmark Proves About Defense-in-Depth

Let’s face it: inertia is often the most common yet most dangerous adversary when it comes to acquiring new technology, especially in cybersecurity.

There is still a persistent assumption across many organizations that email security architecture that worked three years ago is still good enough for today’s threat landscape. Even when security teams suspect gaps, the friction of evaluating, procuring and operationalizing new technology creates a massive organizational bottleneck.

Calculating the true total cost of ownership (TCO) and return on investment (ROI) has historically felt like an exercise in guesswork that often leaves executives, like the CFO, questioning whether the investment is worth it. Vendor claims are notoriously reliant on synthetic lab simulations or cherry-picked sample sizes that rarely survive in an organization’s live environment.

That reality is why Microsoft’s latest benchmark release is an inflection point for organizations looking to evaluate the effectiveness of their tech stack.

Just last week, Microsoft published its fifth consecutive Microsoft email security benchmarking report that analyzed real-world customer telemetry from May - July 2026. This report strips away marketing hyperbole and measures what security tools actually catch inside live production tenants.

The data reveals two fundamental realities:

1. Native cloud defense has matured significantly. Microsoft Defender stops the overwhelming volume of commodity spam, mass phishing and known malware before it reaches an inbox. Routing email via a legacy Secure Email Gateway (SEG) into Microsoft Defender introduces unnecessary cost, latency, technical complexity and operational friction.
   
   
2. Evasive, payload-free attacks demand specialized behavioral AI. Baseline perimeter filtering inevitably leaves an attack surface exposed to executive impersonation and Business Email Compromise (BEC). Hyper-personalized GenAI spear phishing and adversarial prompt injections have also become widespread, targeting users wherever they collaborate, whether in Outlook or Microsoft Teams. Because these attacks contain no malicious attachments or known-bad links, static inspection has nothing to detonate. Stopping them requires behavioral AI that understands communication history, organizational relationships, and conversational context to detect deception before it reaches the inbox.

To understand how the market solves this challenge, Microsoft measured seven leading Integrated Cloud Email Security (ICES) add-on solutions running directly on top of Microsoft Defender.

The result? KnowBe4 Defend ranked #1 across every single uplift metric reported.

When combined with our position as a member of the Microsoft Defender ICES Vendor Ecosystem, this data gives security leaders the clear, verifiable foundation they need to make confident architectural decisions.

100% Microsoft Telemetry: The Data That Cuts Through the Noise

Unlike synthetic vendor tests, Microsoft’s benchmark evaluated real mail delivered across live corporate environments. When measuring how much incremental malicious mail add-ons were caught after Microsoft Defender delivered the message, the figures were unmistakable:

• #1 in Dangerous Email Caught That Microsoft Defender Missed (1.11% vs. 0.30% Field Average):
  KnowBe4 Defend caught 3.7 times more dangerous emails that slipped past Microsoft Defender than the average add-on. Defend stopped nearly 3x more missed threats than the runner-up (Darktrace at 0.38%), roughly 7x more than Proofpoint API (0.16%), and 18x more than Abnormal AI (0.06%).
  
  
• #1 in Active Inbox Clean-Up (16.92% vs. 8.00% Field Average):
  Modern adversaries frequently weaponize links or compromise accounts after delivery. In mailboxes protected by Defend, KnowBe4 was directly responsible for identifying and pulling back 16.92% of all post-delivery malicious removals, more than double the industry average.
  
  
• The Lowest Overlap with Microsoft Defender (0.65%):
  A layered defense must deliver genuine efficacy, not redundant alert fatigue. Defend recorded an overlap of just 0.65% with Defender: the lowest of all seven vendors. This proves Defend identifies evasive, net-new threats rather than taking credit for items Microsoft’s baseline filters had already flagged.
  
  
• Productivity Uplift for Admins and End Users:
  Beyond high-severity attacks, Defend took first place in Spam Uplift (1.88%) and Promotional / Graymail Cleanup (65.24%), reclaiming hours of lost focus across the workforce.

Strategic Partnership vs. Basic Integration: The ICES Vendor Ecosystem Advantage

A common misconception in the email security market is that all API-connected solutions are created equal. In reality, there is a fundamental difference between a vendor that merely connects to Microsoft Graph APIs and one that co-engineers alongside Microsoft product teams.

Dozens of tools can poll an API to pull message headers or trigger an external quarantine. However, operating as an isolated silo often creates detection lag and forces admins into fragmented workflows.

KnowBe4 is a charter member of the Microsoft ICES Vendor Ecosystem. This strategic relationship represents a shared engineering vision between Microsoft and KnowBe4:

• Architectural Co-Engineering: Building on our long-standing collaboration, such as joint engineering on the Phish Alert Button (PAB) for Microsoft Outlook and Microsoft Teams, our teams collaborate on native telemetry exchange and synchronized threat mitigation.
  
  
• Designed for Co-Existence: Microsoft created the ICES ecosystem specifically because modern cloud environments require specialized behavioral AI layers that work seamlessly alongside Microsoft Defender, rather than competing with it for mail control.
  
  
• A Roadmap of Continuous Alignment: Ecosystem participation ensures KnowBe4 Defend evolves in lockstep with Microsoft’s underlying architecture, ensuring zero disruption to mail flow and ensures customers are getting the latest in innovation as it happens across both platforms.

Maximizing Your Investment: Microsoft Defender Is the Foundation, Not the Finish Line

When organizations standardize on Microsoft 365, security leaders face a common dilemma: If we're already invested in Microsoft, is native Defender enough?

Across many enterprises, the prevailing assumption has been that upgrading licensing tiers or relying solely on built-in tools would check every security box.

Microsoft Defender provides an exceptional foundation for baseline hygiene, static detonation and perimeter filtering. It eliminates the overwhelming noise of commodity attacks so your team doesn't have to. The data is confirming the industry trend of moving away from a SEG and layering your foundational platform with an ICES offering such as Defend for better efficacy, increased productivity for SOC analysts and an accelerated time to value.

For organizations, the winning strategy isn't relying on a single layer, it is amplifying the native investment you've already made. By layering KnowBe4 Defend directly on top of Microsoft Defender via native Graph APIs or pre-delivery inline deployment, security teams get the best of both worlds: Defender handles the high-volume perimeter baseline, while Defend targets the high-risk blind spots that native filters cannot solve alone:

• Conversational and Behavioral Anomalies: Neutralizing executive impersonation and invoice fraud containing zero malicious links, malware or known-bad infrastructure.
  
  
• Adversarial AI and Model Diversity: Defending against polymorphic AI spear phishing and prompt manipulation engineered to bypass perimeter defenses.
  
  
• Microsoft Teams and Collaboration Posture: Understanding lateral threat movement from email to Microsoft Teams channels and chats, where legacy email gateways cannot see. With the ability to monitor and remediate the impact insecure Microsoft Teams settings can have on your environment.
  
  
• Point-of-Risk User Coaching: Pairing machine-speed AI verdicts with contextual, color-coded and localized teachable moments that guide employees at the exact moment risk appears.

The Clear Blueprint for Security Leaders

If your team is reviewing its email and collaboration security strategy, Microsoft’s latest benchmark and our joint ecosystem integration make the path forward straightforward:

1. Stop paying twice for redundant gateway infrastructure. Continuing to fund an expensive legacy SEG (like Mimecast or Proofpoint) while paying for Microsoft 365 licensing increases operational costs, introduces latency and misses high-severity attacks.
   
   
2. Maximize your existing Microsoft investment. Leverage Microsoft Defender’s baseline strength and augment it with the ICES partner proven to deliver the highest incremental detection rate on Microsoft’s own platform.
   
   
3. Base your ROI on real-world telemetry. Eliminate procurement guesswork by relying on verifiable production telemetry and native architectural alignment.

Experience the Better Together Architecture

Discover how KnowBe4 Defend and Microsoft Defender collaborate under the hood to deliver airtight protection:

• Read the Benchmark Report: Explore Microsoft’s findings directly on the Microsoft Security Blog.
• Schedule a 10-Minute Demo: See how Defend connects natively into your Microsoft 365 environment. Request a live demo.
• Join the Upcoming Webinar (October 28): Hear from Stuart Clark, SVP of Product at KnowBe4, as he deconstructs the benchmark findings, demonstrates live KQL threat hunting, and outlines our joint roadmap with Microsoft.