Summary
To identify how Microsoft domains contribute to IP blocks in SNDS, it is crucial to understand that SNDS provides a consolidated, aggregated view of your IP's reputation across Microsoft's entire email network. It does not break down block data by individual domains like hotmail.com or outlook.com. Instead, a block indicated in SNDS signifies that Microsoft's unified filtering system, which applies across all its properties, is responsible for the deliverability issue. Key metrics within SNDS, such as the 'Blocked IPs' tab, 'Junk Mail Complaints', and 'Spam Trap Hits', reflect the overall health and perception of your sending IP by Microsoft's collective systems, allowing senders to diagnose and attribute issues to Microsoft's overarching policies and infrastructure.
Key findings
- SNDS Provides Consolidated View: Microsoft's Sender Network Data Services (SNDS) offers a single, aggregated view of an IP's reputation and block status across its entire network of domains. It does not itemize or list individual Microsoft domains (e.g., hotmail.com, outlook.com) that contribute to specific blocks.
- Unified Block Application: When an IP is blocked according to SNDS, it means the block is applied across Microsoft's unified filtering infrastructure, impacting deliverability to all Microsoft-managed domains. This reflects the collective assessment of Microsoft's systems.
- Metrics Indicate Network-Wide Issues: The 'Junk Mail Complaints' and 'Spam Trap Hits' metrics within SNDS directly indicate how your mail is perceived by Microsoft's filters across its entire email ecosystem. High volumes in these areas, especially when an IP is blocked, signal that Microsoft's internal systems are actively flagging your mail.
Key considerations
- Leverage SNDS: Regularly monitor the Microsoft Sender Network Data Services (SNDS) portal as your primary tool for diagnosing IP reputation and block status with Microsoft. This platform provides a consolidated view of your sending health across all Microsoft properties.
- Review Key Metrics: Pay close attention to the 'Blocked IPs' tab, 'Junk Mail Complaints', and 'Spam Trap Hits' within SNDS. These metrics are crucial indicators of how your mail is perceived by Microsoft's collective filtering systems and directly reflect user and system feedback from across their entire network of domains.
- Understand Unified Filtering: Recognize that if an IP is listed as blocked or shows poor reputation in SNDS, it signifies a block applied consistently across Microsoft's unified email infrastructure, encompassing all their consumer domains like Outlook.com, Hotmail, and Live. Microsoft does not provide a breakdown by individual domains within SNDS.
What email marketers say
10 marketer opinions
Identifying which Microsoft domains contribute to IP blocks in SNDS primarily involves understanding the platform's unified approach. Microsoft's Sender Network Data Services (SNDS) provides a single, overarching assessment of your IP's reputation across its entire email infrastructure, encompassing properties like Outlook.com, Hotmail, Live, and MSN. Crucially, SNDS does not itemize blocks or filtering decisions by individual domains; rather, any block or negative reputation indicated reflects a collective judgment by Microsoft's network-wide systems. Senders should focus on key metrics such as the 'Blocked IPs' tab, 'Junk Mail Complaints', and 'Spam Trap Hits' within SNDS, as these directly signal how your mail is perceived by Microsoft's comprehensive filters and indicate their contribution to any deliverability issues.
Key opinions
- Unified Reputation View: SNDS offers a holistic view of your IP's reputation across all Microsoft properties, rather than breaking down data by specific domains such as Outlook.com or Hotmail.
- Network-Wide Blocks: When an IP is listed as blocked in SNDS, it indicates a block applied consistently across Microsoft's entire email ecosystem, meaning all Microsoft-managed domains are affected.
- Key Metric Indicators: Metrics like 'Junk Mail Complaints' and 'Spam Trap Hits' within SNDS are direct signals of how your email is perceived by Microsoft's collective filters and contribute to network-wide deliverability decisions.
- No Individual Domain Breakdown: Senders will not find a breakdown of filtering decisions or blocks by separate Microsoft domains within the SNDS portal; the data is aggregated.
Key considerations
- Prioritize SNDS Monitoring: Regularly use Microsoft's Sender Network Data Services (SNDS) as the definitive tool for assessing your IP's health and understanding Microsoft-specific blocks.
- Analyze Core Metrics: Diligently review 'Junk Mail Complaints', 'Spam Trap Hits', and the 'Blocked IPs' status within SNDS, as these are the primary indicators of issues from Microsoft's network.
- Interpret Unified Feedback: Understand that any negative status in SNDS reflects a unified decision by Microsoft's filtering systems across all its consumer domains, requiring a holistic approach to remediation.
- Utilize External Tools for MX Records: While SNDS provides an aggregated view, some deliverability dashboards can identify numerous domains using Outlook.com MX records, offering a broader context for Microsoft's presence in your recipient list.
Marketer view
Email marketer from Email Geeks shares that his internal data shows over 100 different domains using Outlook.com MX in the past month, including many regional domains, which he identifies using a deliverability dashboard that filters by MX.
26 May 2025 - Email Geeks
Marketer view
Email marketer from Mailgun explains that Microsoft SNDS provides a 'health check' on your sending IPs specifically from Microsoft's perspective across its entire network of domains (Outlook.com, Hotmail, MSN). The data within SNDS, such as junk mail complaints, spam trap hits, and reputation scores, directly reflects Microsoft's assessment. By monitoring these metrics, senders can understand the specific issues that lead to blocks and which IPs are affected, thus identifying Microsoft's contribution to deliverability issues.
26 May 2022 - Mailgun
What the experts say
2 expert opinions
To fully grasp how Microsoft domains influence IP blocks reported in SNDS, it's essential to recognize the platform's aggregated nature. While Microsoft's Smart Network Data Services (SNDS) delivers consolidated reputation data for an IP across its vast network, it intentionally omits a breakdown by individual domains like hotmail.com or outlook.com. Furthermore, SNDS does not encompass data from Office 365 environments. For a comprehensive understanding, senders must look beyond SNDS's unified view and perform MX record lookups to identify the true breadth of domains, many more than commonly assumed, that utilize Microsoft's mail exchange services. This deeper investigation is crucial since an IP could still be actively sending through automated systems despite a block.
Key opinions
- SNDS Aggregation: Microsoft's SNDS provides reputation and block data for an IP address as an aggregate across its entire network, without offering specific breakdowns for individual Microsoft domains.
- Hidden Microsoft Domains: Many more domains than commonly realized point to Microsoft MX records, ranging from 29-93 in some client data, which are part of the larger Microsoft network but not individually detailed in SNDS.
- SNDS Omission of O365: The data available through SNDS does not include deliverability insights related to Office 365 (O365) environments.
- Persistent Automated Sending: Even when an IP is subject to blocks, automated systems might continue sending email, which can influence deliverability metrics.
Key considerations
- Expand Domain Discovery: To understand the full scope of Microsoft's impact, conduct MX record lookups to identify all domains that route mail through Microsoft's infrastructure, extending beyond common consumer domains.
- Account for O365 Blind Spots: Recognize that SNDS does not provide visibility into deliverability performance or blocks specifically within Microsoft's Office 365 ecosystem.
- Monitor Automated Flows: Be aware that automated sending systems linked to an IP may continue operation even if a block is in place, requiring ongoing monitoring and adjustment.
- SNDS for Network-Wide View: Leverage SNDS for its comprehensive, network-wide perspective on IP reputation, understanding that it reports on the collective Microsoft network without domain-specific granularity for blocks.
Expert view
Expert from Email Geeks explains that an IP might still be sending via automated systems, and that senders need to look up all domains by MX records because many more domains than commonly known point to Microsoft MXs (e.g., 29-93 domains found in her client data) and SNDS does not look at O365 data.
3 Jul 2023 - Email Geeks
Expert view
Expert from Word to the Wise explains that Microsoft's Smart Network Data Services (SNDS) provides reputation data and statistics for IP addresses sending to Microsoft's network. However, SNDS does not offer a breakdown of data by individual Microsoft domains, such as hotmail.com or outlook.com, contributing to IP blocks. Instead, the data presented in SNDS is aggregated for the entire Microsoft network, focusing on metrics like complaint rates, spam trap hits, and sender reputation for a given IP address.
11 Jan 2023 - Word to the Wise
What the documentation says
3 technical articles
The Microsoft Sender Network Data Services (SNDS) portal serves as the definitive resource for diagnosing IP blocks from Microsoft's email infrastructure. While SNDS offers a unified view of your IP's status across their entire network, it crucially indicates whether your IP is blocked and provides the specific reason for such blocks. This consolidated data reflects the overall health of your sending reputation as perceived by all Microsoft properties, without listing individual contributing domains. By reviewing the IP reputation and block status, along with the stated reasons within SNDS, senders can identify if their IPs are affected by Microsoft's systems and understand the underlying causes based on their network-wide filtering policies.
Key findings
- SNDS Shows Consolidated View: The Microsoft Sender Network Data Services (SNDS) portal provides a consolidated view of your IP's reputation across Microsoft's entire network of email properties, rather than breaking down block data by individual domains.
- Block Reasons Are Provided: SNDS explicitly indicates if your IP address is blocked and provides the reason for the block, such as policy violations, high spam complaints, or spam trap hits.
- Blocks Apply Network-Wide: A block identified in SNDS means the issue is applied across Microsoft's unified filtering infrastructure, impacting deliverability to all Microsoft-managed domains, signifying a network-wide assessment.
- Filtering Criteria Influence Blocks: Microsoft's deliverability best practices detail the criteria that influence filtering and contribute to IP blocks visible in SNDS, reflecting the assessment of their overarching systems encompassing all domains.
Key considerations
- Monitor SNDS Regularly: Consistently check the Microsoft Sender Network Data Services (SNDS) portal, as it is the primary tool for diagnosing your IP's reputation and block status with Microsoft.
- Focus on Block Reasons: When reviewing SNDS, pay close attention to the 'Blocked IPs' tab. This section not only indicates if your IP is blocked but also provides the specific reason, such as policy violations or spam trap hits, which is vital for effective remediation.
- Understand Network-Wide Impact: Recognize that a block identified in SNDS applies across Microsoft's entire email infrastructure, affecting deliverability to all their domains (e.g., Hotmail.com, Outlook.com), even though individual domains are not listed.
- Align with Best Practices: Familiarize yourself with Microsoft's email deliverability best practices for Office 365, as these guidelines explain the filtering criteria that lead to IP blocks and help prevent future issues across their network.
Technical article
Documentation from learn.microsoft.com explains that Outlook.com Postmaster Tools and its Sender Network Data Services (SNDS) portal are crucial for understanding your IP's reputation with Microsoft. While SNDS does not explicitly list individual Microsoft domains (e.g., hotmail.com, outlook.com) that contribute to blocks, it provides a consolidated view of your IP's status across their entire network. By reviewing the IP reputation and block status within SNDS, senders can identify if their IPs are blocked by Microsoft's systems and the overall health of their sending reputation as seen by all Microsoft properties.
21 Jun 2023 - learn.microsoft.com
Technical article
Documentation from support.microsoft.com clarifies that if your IP address is blocked by Microsoft, the SNDS portal is the primary tool for diagnosis. It states that the 'Blocked IPs' tab in SNDS shows any of your sending IP addresses that are currently blocked, along with the reason for the block (e.g., policy violations, high spam complaints, spam trap hits). This consolidated data implicitly identifies the contribution of Microsoft's entire email infrastructure, as blocks are applied across their network of domains.
3 Aug 2022 - support.microsoft.com
How to get Microsoft SNDS access when using an Email Service Provider?
How to identify and manage domains protected by Cloudmark?
How to resolve email blocking issues with Microsoft domains?
What are the common issues with Microsoft SNDS (Sender Network Data Services)?
What Microsoft domains should I exclude from my email segmentation?
Why are IPs listed as blocked on SNDS with no Microsoft bounces?
