Why do ESPs deny SNDS access and what are the risks?
Michael Ko
Co-founder & CEO, Suped
Published 24 May 2025
Updated 16 Aug 2025
7 min read
Microsoft's Smart Network Data Services (SNDS) provides valuable insights into email sending reputation, particularly for mail sent to Outlook.com and other Microsoft domains. It allows senders to monitor their IP reputation, spam complaint rates, and other critical metrics. However, many Email Service Providers (ESPs) do not grant their customers direct access to SNDS data, even for those using dedicated IP addresses. This denial often raises questions and concerns among email marketers and deliverability professionals.
Understanding why ESPs choose to restrict this access and the potential risks it poses for email senders is crucial for managing email deliverability effectively. This includes considering the ESP's operational needs, data privacy concerns, and the unique challenges associated with managing IP ownership and access to sensitive reputation data.
Reasons for restricted access to SNDS
ESPs often deny direct SNDS access primarily because they own and manage the IP addresses from which emails are sent. This ownership means they are ultimately responsible for the overall reputation and health of those IPs. Granting direct, unrestricted access to individual customers could complicate their operational management and potentially expose proprietary data or impact other clients on shared infrastructure.
Beyond mere ownership, ESPs also cite data privacy and security as significant concerns. SNDS data can contain sensitive information about sending patterns and potentially aggregate data from multiple users on a given IP, especially if it's a shared IP environment. Directly sharing this could inadvertently expose data related to other customers using the same IP space, leading to potential privacy breaches.
Moreover, managing SNDS access for a large number of diverse clients can introduce considerable operational complexities. Each request would require validation and ongoing management, which can be resource-intensive. While some third-party deliverability tools might offer aggregated data, directly managing granular SNDS access for every customer can be a heavy burden for ESPs, making a blanket denial a simpler operational choice for many.
This practice is not uncommon, as many ESPs aim to centralize control over critical sending infrastructure. This approach allows them to proactively manage issues, respond quickly to emerging threats, and maintain a consistent sending reputation across their entire network, benefiting all their clients in the long run.
ESP's perspective
ESPs own the IP addresses used for sending emails. Granting direct SNDS access means relinquishing some control over these critical assets, which can impact their broader network reputation and potentially other clients sharing IPs.
SNDS reports contain aggregated data that might reveal patterns across multiple senders on the same IP. ESPs aim to protect this aggregated data and ensure that no single client's access compromises the privacy or security of others. This is a primary driver behind their security concerns regarding PII, or Personally Identifiable Information.
Sender's perspective
Senders require full visibility into their email performance. Without direct access to SNDS, they are blind to critical metrics directly from Microsoft, hindering proactive deliverability management and quick issue resolution.
Relying solely on ESP-provided data can be limiting. Senders prefer to independently verify their reputation and diagnose issues using primary data sources like SNDS data to ensure accurate and timely insights into their email program.
The challenge of revoking access
One of the significant technical hurdles for ESPs is the perceived difficulty in revoking SNDS access once it has been granted. While SNDS does offer a "request reauthorization" button, which can trigger re-validation for a user with IP access, this process can be complex. An end-user with access might theoretically be able to initiate a re-validation that could remove IPs from the ESP's own SNDS account if the process is not completed correctly or in a timely manner.
This lack of straightforward revocation mechanisms presents a risk, particularly when a customer transitions away from an ESP. If a customer has direct SNDS access to IPs previously used, there is no inherent mechanism within SNDS itself to prohibit them from continuing to see data for those IPs even after their brand no longer uses them. This ongoing visibility could pose competitive or data privacy risks for the ESP and its new clients on those IPs.
The challenge of controlling access is amplified in environments where IPs are reused or shared among multiple clients. Even with dedicated IP addresses for a single customer, the ESP often maintains a pool of IPs, and the rotation or reassignment of these IPs means that previous access grants could become problematic. This situation contributes to ESPs' reluctance to grant direct access, preferring instead to manage this critical data internally.
For email senders, being denied direct SNDS access means a significant loss of transparency into their own email performance with Microsoft email services. Without direct access, senders cannot independently verify their sender reputation metrics, such as spam complaint rates and blocklist (or blacklist) listings, as reported directly by Microsoft. This creates a reliance on the ESP for critical deliverability insights, which may not always be as granular or real-time as needed.
The primary risk is a lack of granular insight. SNDS provides detailed data on specific IP addresses, allowing senders to identify precise issues like traffic spikes, sudden drops in reputation, or increased spam trap hits. Without this direct visibility, senders are less able to proactively diagnose and address deliverability problems, leading to potential delays in issue detection and resolution.
Furthermore, senders become entirely dependent on their ESP's reporting and responsiveness for understanding their Microsoft deliverability. While many ESPs provide their own dashboards or reports, these may not always align with the raw SNDS data or provide the necessary detail to pinpoint root causes of deliverability challenges. This dependency can hinder a sender's ability to optimize their email program and maintain high inbox placement rates.
This situation is particularly challenging for senders using shared IP pools, where the actions of other users can impact their own reputation without immediate, clear insight. Understanding what happens when your domain is on an email blacklist or an IP blocklist is vital, even if direct SNDS access is not available. The inability to check Microsoft SNDS data for Amazon SES is a common example of this type of limitation.
Views from the trenches
Best practices
Maintain strong sending hygiene, regardless of SNDS access, by managing your lists and monitoring engagement.
Regularly request comprehensive deliverability reports from your ESP, focusing on Microsoft-specific metrics.
Implement robust email authentication protocols, including DMARC, SPF, and DKIM.
Actively monitor your sender reputation using publicly available blocklist (or blacklist) checkers.
Common pitfalls
Assuming your ESP provides all necessary deliverability data, leading to blind spots.
Neglecting other reputation monitoring tools because you believe SNDS is the only source.
Not understanding the implications of shared versus dedicated IP addresses on SNDS access.
Failing to document and understand your ESP's policy on SNDS data sharing before signing up.
Expert tips
Some ESPs provide an API or a summary dashboard that consolidates SNDS-like data, which can be a good alternative.
For specific troubleshooting, ask your ESP to pull raw SNDS logs for your dedicated IPs.
Consider engaging a deliverability consultant if you suspect issues and your ESP cannot provide sufficient data.
Focus on proactive list hygiene to minimize negative signals like spam complaints.
Marketer view
Marketer from Email Geeks says they don’t offer direct SNDS access based on their discussions with the ESP.
2023-03-06 - Email Geeks
Expert view
Expert from Email Geeks says SNDS is not always useful, suggesting its data can be limited.
2023-03-06 - Email Geeks
Balancing control and transparency
The decision by many ESPs to deny direct Microsoft SNDS access is a complex issue driven by a combination of IP ownership, security considerations, operational overhead, and the challenge of access revocation. While understandable from an ESP's perspective, this policy places a significant burden on senders who lose direct visibility into crucial reputation data.
For senders, understanding these limitations is key. It's important to engage with your ESP to understand what reputation data they can provide and how often. While direct SNDS access may not always be feasible, a robust communication channel and transparent reporting from your ESP can help mitigate some of the risks associated with this restricted access. This open dialogue is crucial for effective email deliverability.
Ultimately, the goal is to ensure your emails reach the inbox effectively. By focusing on strong sending practices, utilizing available reporting, and maintaining clear communication with your ESP, senders can navigate these challenges and optimize their email programs, even without direct access to all data sources.
SNDS, they are blind to critical metrics directly from Microsoft, hindering proactive deliverability management and quick issue resolution.
