How should I group Microsoft email provider data for deliverability reporting?

Key findings

• Distinct platforms: Outlook.com (including Hotmail, Live, etc.) and Microsoft 365 (M365) represent two different ecosystems with varying filtering rules and reputation considerations. Consumer mail is typically handled by MX records like *.olc.protection.outlook.com, while business mail uses *.mail.protection.outlook.com.
• Varied remediation paths: The avenues for addressing deliverability issues, such as feedback loops (FBLs) and postmaster support, often differ between the consumer and commercial platforms. For example, Microsoft's Smart Network Data Services (SNDS) provides valuable data primarily for consumer domains. You can learn more about how reliable SNDS data is.
• Actionable insights: Grouping data by specific Microsoft segments (e.g., Outlook Consumer vs. M365) allows for a more granular understanding of performance issues like bounce rates and FBLs. This granularity enables teams to take targeted action on specific accounts or sending practices impacting deliverability to a particular segment. Understanding effective strategies for resolving deliverability issues is key.
• Evolving MX records: Microsoft's MX records can change or expand (e.g., mail.messaging.microsoft.com, *.mx.microsoft), requiring continuous monitoring. For a sampling of O365 MX records, refer to Wombatmail's MX records for Outlook.com.

Key considerations

• Reporting objectives: The level of detail needed depends on your goals. For high-level trends, a broader 'Microsoft' grouping might suffice. For in-depth troubleshooting or strategic adjustments, granular data is essential.
• Data collection complexity: Collecting and segmenting data by specific MX records or Microsoft subgroups can add complexity to your reporting infrastructure, but it provides greater accuracy.
• Impact on sender reputation: A decline in deliverability to one Microsoft segment may not immediately reflect in others, but consistent negative trends across all segments can indicate broader reputation issues.
• Resource allocation: Consider the resources available for data analysis and the subsequent actions your team can take based on highly detailed reports.

Key opinions

• Unified view for initial assessment: Many marketers prefer to initially view all Microsoft domains together for a high-level overview of overall performance before drilling down into specifics. This helps in quick identification of widespread issues affecting the entire Microsoft ecosystem.
• Action-oriented segmentation: Segmentation is most valuable when it directly leads to actionable steps, such as pausing sends to specific problematic segments or adjusting content strategies for certain recipient groups. Learn how to improve deliverability to Microsoft.
• Bounce and FBL focus: Monitoring bounce rates and feedback loop complaints across different Microsoft domains is a primary concern, as these metrics directly indicate deliverability health and potential blacklist risks. You can use a blocklist checker to see if you're listed.
• Impact of new requirements: Recent updates to Microsoft's sender requirements (especially for high-volume senders) make granular data more critical for ensuring compliance and avoiding blanket filtering. Acoustic provides guidance on preparing for these changes.

Key considerations

• Audience segmentation: Consider if your audience segments align with Microsoft's internal domain groupings. For example, are your B2B customers primarily on M365 domains and B2C on Outlook.com?
• Reporting tool capabilities: Ensure your email service provider (ESP) or analytics platform can support the desired level of granularity for Microsoft domains without extensive manual effort.
• Campaign performance: Evaluate if differing deliverability to Microsoft segments has a noticeable impact on campaign open rates, click-through rates, or conversion metrics.
• Feedback loops: While grouping by MX can be useful, marketers must ensure they are properly registered for relevant feedback loops (FBLs) across all Microsoft properties to receive complaint data.

Key opinions

• MX record-level granularity: It is essential to segment data based on the specific Mail Exchanger (MX) records, distinguishing between consumer services (Outlook.com, Hotmail) and commercial services (Microsoft 365, Exchange Online). Their filtering logic and reputation systems are often separate. You can learn more about how to identify Microsoft owned inboxes.
• Authentication standards: Microsoft has stringent authentication requirements (SPF, DKIM, DMARC), and issues like an SPF DNS timeout or DKIM temporary errors can manifest differently across segments. Granular data helps pinpoint the exact cause.
• Specialized postmaster engagement: Interacting with Microsoft to resolve deliverability issues (e.g., blocklist removals, reputation inquiries) often requires understanding which specific Microsoft service is affected, as each may have its own designated support channels or tools.
• Proactive monitoring: Newer MX records or sub-domains might emerge, and monitoring these separately can provide early warnings of reputation changes or filtering adjustments by Microsoft. This proactive approach helps in maintaining consistent deliverability.

Key considerations

• Behavioral differences: Consumer services (like Outlook.com) are more sensitive to spam complaints and user engagement, while business services (M365) might have stricter authentication and compliance checks.
• Data aggregation strategy: While granular data is valuable, consider establishing a clear aggregation strategy for higher-level reporting to avoid analysis paralysis. You might group sub-segments into broader categories for weekly reports, but maintain the granular data for deep dives.
• Tool integration: Ensure your deliverability monitoring tools can effectively break down Microsoft data by the required MX segments, rather than just a generic 'Microsoft' category.
• Compliance changes: Stay informed about Microsoft's evolving sender requirements, as these can dictate new needs for data segmentation and reporting. Recent changes (like those in May 2025) underline this necessity.

Key findings

• Separate guidelines for bulk senders: Microsoft publishes distinct sets of guidelines and best practices for senders targeting Outlook.com (consumer) and those sending to Microsoft 365 (business) tenants. These can cover authentication, content, and sending volume. Microsoft's Tech Community outlines new sender requirements.
• Authentication enforcement: Both Outlook.com and M365 rigorously enforce email authentication (SPF, DKIM, DMARC), with specific nuances in how alignment is treated for each service. Reporting should verify proper authentication for each segment.
• Distinct feedback mechanisms: The primary feedback mechanism for consumer-facing services is SNDS (Smart Network Data Service), providing insights into reputation and complaints. For M365, administrators typically rely on the Exchange Online Protection (EOP) and Microsoft Defender for Office 365 (MDO) reporting within their admin portals.
• Reputation segregation: While an IP or domain's overall reputation influences both, the filtering decisions and reputation scores can be calculated differently or have varying impacts across Outlook.com versus Microsoft 365. For example, a high volume of spam complaints on Outlook.com might not immediately or equally impact deliverability to M365 inboxes.

Key considerations

• Compliance monitoring: Reports should be structured to show compliance with Microsoft's varying sender requirements across its platforms. This includes adherence to their new bulk sender guidelines implemented in 2025.
• Bounce code analysis: Detailed analysis of bounce codes for each Microsoft segment can provide specific clues about why emails are not being delivered (e.g., policy blocks, content filtering, reputation issues).
• Spam trap hits: Understanding if spam trap hits occur disproportionately in one Microsoft segment over another can inform list hygiene strategies. For more information, read our guide to spam traps.
• Impact of shared IPs: If using shared IPs, granular Microsoft data can help identify if deliverability issues are isolated to a specific segment due to the sending practices of other users on that shared IP, allowing for targeted mitigation efforts.