Microsoft has released its fourth consecutive quarterly email security benchmarking report, completing a full year of real-world performance comparisons between Microsoft Defender and competing email security vendors. The program, which began with its first report in July 2025, measures Defender against both secure email gateway vendors, known as SEGs, and integrated cloud email security vendors, known as ICES, using production threat telemetry rather than synthetic tests.
The four-quarter dataset has produced three findings that have held across each reporting period. On pre-delivery detection, Defender has missed fewer high-severity threats than every SEG vendor evaluated in all four quarters. The next-closest SEG vendor recorded 2.5 times more misses than Defender across that period. For the most recent quarter, Defender missed 59 percent fewer high-severity threats than the next-closest SEG competitor, a gap Microsoft says has remained consistent across all four periods.
For ICES vendors, which operate on top of Defender rather than replacing it, the data shows their clearest contribution is in promotional and bulk mail filtering. Across the four quarters, ICES vendors delivered an average uplift of 15 percent in promotional filtering. Their contribution to malicious message detection averaged 0.29 percent uplift and spam catch averaged 0.68 percent uplift, both of which Microsoft reports have trended downward over the last three quarters. In the most recent period, ICES vendors delivered an average improvement of 16.85 percent in promotional and bulk mail filtering, while average improvement for malicious messages was 0.13 percent and for spam was 0.28 percent.
The most significant shift across the year is in post-delivery remediation. When Microsoft introduced post-delivery catch metrics in its second report, Defender accounted for 45 percent of post-delivery malicious catch. That figure has since risen to an average of 96 percent. In the most recent quarter, Defender's post-delivery catch rate reached 96.03 percent, up from 70.8 percent the prior quarter. Post-delivery remediation covers threats that reach users' inboxes and are subsequently identified and removed.
Microsoft also disclosed several product changes it attributes to the benchmarking program. A dedicated Promotions folder for Outlook is in development and will be enabled by default once it reaches general availability, separating bulk and newsletter content from primary inboxes without routing it to Junk. In November 2025, Microsoft introduced an agentic grading system into its email submission and analysis pipeline to reduce manual review and accelerate response times when security teams submit emails for analysis.
A separate tool, the Microsoft Security Copilot Alert Triage Agent, uses language model-based reasoning to classify user-reported phishing emails, resolve false positives and escalate confirmed threats. Microsoft reports that analysts using the tool identify 6.5 times more malicious alerts, achieve 77 percent higher verdict accuracy, and spend 53 percent more time investigating confirmed threats compared to working without it. A companion feature called Security Copilot Email Summary converts email detection data into summaries within the email entity page to support faster investigation.
Microsoft also said it has established what it calls the Microsoft Defender ICES vendor ecosystem, a program designed to allow integration between Defender and third-party ICES vendors to support organizations running multi-vendor email security configurations.
By: Jeff Pinkston, Vice President and General Manager, Microsoft Defender for Office 365
