What are the common issues with Microsoft SNDS (Sender Network Data Services)?
Matthew Whittaker
Co-founder & CTO, Suped
Published 10 Jun 2025
Updated 17 Aug 2025
7 min read
Microsoft's Sender Network Data Services (SNDS) is an invaluable, free tool designed to provide senders with insights into their email sending reputation and deliverability to Outlook.com users. It offers data on spam complaints, junk mail reporting program (JMRP) feedback, and IP blocklist status, all crucial for maintaining healthy email sending. However, accessing and interpreting this data is not always straightforward, and senders often encounter common issues that can hinder their deliverability efforts.
Navigating SNDS can be a significant challenge, even for experienced email professionals. From data discrepancies to access hurdles, the platform sometimes presents more questions than answers. Understanding these common problems is the first step toward effective troubleshooting and ensuring your messages reach the inbox.
This guide will walk you through the frequent issues faced when using Microsoft SNDS, offering insights into why they occur and how to approach them effectively.
Access and data display challenges
A primary frustration for many senders revolves around gaining and maintaining access to SNDS, as well as the reliability of the data displayed. The process of registering IPs and domains can be cumbersome, and even once access is granted, the data is not always immediately available or up to date.
One common issue is the delayed or non-receipt of authorization emails, which are crucial for verifying ownership and gaining access. This can leave senders in limbo, unable to view critical reputation data. This problem is particularly prevalent for those using email service providers (ESPs) with shared IPs, where gaining direct access can be complicated. Sometimes, SNDS authorization emails are delayed or don't arrive at all, creating a significant hurdle. Furthermore, limitations exist for some ESPs, such as Amazon SES, regarding SNDS access, requiring alternative monitoring methods.
Even when you have access, senders frequently report that SNDS data isn't displaying or is significantly delayed. This can be due to system maintenance or technical glitches on Microsoft's end. Without real-time or even consistently fresh data, it's difficult to react quickly to deliverability issues, leaving email programs vulnerable to prolonged inboxing problems. This lack of transparency can be particularly frustrating during critical sending periods.
SNDS portal access and functionality issues
Unexpected downtime or intermittent access to the SNDS portal itself is a recurring complaint among senders. While temporary, such outages prevent immediate access to critical data and insights needed for troubleshooting. Even when the portal is back online, residual issues like delayed authorization emails can persist, impacting timely access. Microsoft's Sender Support FAQ mentions general guidance for deliverability, but real-time status updates for SNDS can be scarce.
Discrepancies and misleading data
Perhaps one of the most confusing issues is when SNDS data appears healthy, but deliverability to Microsoft (Outlook.com, Hotmail, Live.com) domains remains problematic. This disconnect can lead to significant troubleshooting headaches.
It's not uncommon for SNDS to show an IP as "green" or "normal" even when emails are consistently landing in junk folders or being blocked outright. This inconsistency is a major pain point, especially during IP warming periods, where accurate feedback is vital. The data might not always reflect the granular reasons for filtering, such as content-based issues or reputation factors outside of the reported metrics. In these cases, it can be hard to resolve email blocks when SNDS shows normal status.
Another specific example is when IPs are listed as blocked on SNDS, but no corresponding bounce messages are received. This silent dropping of emails makes diagnosing problems incredibly difficult, as senders have no immediate indication of delivery failure beyond the SNDS portal. It highlights that SNDS data, while useful, may not provide the complete picture for inconsistent deliverability.
SNDS reported status
IP Status: Often shown as "green" or "normal", suggesting good health.
Complaint Rate: Reported as very low or non-existent, typically below 0.1%.
Spam Trap Hits: Indicated as zero or minimal, implying a clean mailing list.
Actual deliverability experience
Inbox Placement: Emails frequently land in the junk or spam folder, or are not received at all.
Blocklisting: Emails are outright rejected or blocked by Microsoft, despite no block indication in SNDS.
Engagement: Low open and click rates, suggesting poor inboxing even without overt blocks.
Technical and setup pitfalls
While SNDS primarily reports on IP reputation, underlying technical issues with email authentication protocols can severely impact deliverability to Microsoft domains. SNDS might not explicitly flag these, making them harder to diagnose.
Improperly configured SPF, DKIM, or DMARC records are frequent culprits behind deliverability issues, even if SNDS shows a clean IP. Microsoft has strict requirements for email authentication, and failure to meet these can result in messages being rejected or sent to spam. For instance, an authentication setup problem often results in 515 errors, signaling that emails may be silently dropped if misconfigured. It's essential to understand why your emails fail at Microsoft due to hidden SPF DNS timeouts.
Example SPF Record (potential issue: too many lookups)TXT
Beyond authentication, general email server misconfigurations can also lead to deliverability issues that SNDS might not fully illuminate. Things like incorrect reverse DNS (rDNS) entries, or using IPs not registered in SNDS, can cause blocks or junk folder placement. Monitoring your overall email sending reputation requires looking beyond SNDS and at your entire email infrastructure.
Sender reputation and content problems
Even with perfect technical setup, a poor sender reputation or problematic email content can lead to delivery failures. SNDS provides some metrics, but the nuances of reputation management extend beyond its direct reporting.
High spam complaint rates, even if only slightly above Microsoft's acceptable thresholds, can quickly degrade an IP's standing. While SNDS shows complaint rates, it doesn't always provide the context of spam trapsor other nuanced reputation metrics. Sending to outdated or invalid email addresses can lead to increased bounces and eventually, blocklistings (or blacklistings), impacting your sender score. This emphasizes the importance of list hygiene.
Content issues, such as using spammy keywords, suspicious links, or deceptive subject lines, can also trigger Microsoft's spam filters, irrespective of IP reputation. While not directly an SNDS issue, these factors contribute to the overall deliverability problems that senders might incorrectly attribute solely to SNDS data anomalies. Email servers that are misconfigured, particularly with spam filters and SPF/DKIM setups, also commonly lead to silent email drops.
Silent email dropping
A concerning aspect of Microsoft's email filtering is the phenomenon of silently dropping emails. This means messages are not delivered and no bounce-back notification is sent to the sender, making it incredibly difficult to detect deliverability issues without proactive monitoring. While SNDS provides data, it doesn't always show every instance of a silently dropped email, requiring senders to rely on other methods to verify inbox placement.
Views from the trenches
Best practices
Actively monitor all email authentication protocols (SPF, DKIM, DMARC) to ensure proper configuration and alignment.
Implement a comprehensive list hygiene strategy to reduce bounces, spam traps, and improve recipient engagement.
Beyond SNDS, utilize diverse deliverability tools for a holistic view of your sender reputation and inbox placement.
Common pitfalls
Solely relying on SNDS's 'green' status can be misleading when actual deliverability issues persist.
Delaying investigation into deliverability problems when SNDS data is missing or appears contradictory.
Ignoring the impact of content quality, sending frequency, and list segmentation on overall sender reputation.
Expert tips
Prioritize recipient engagement and build a positive sender reputation through consistent, valuable communication.
Proactively test email delivery to Microsoft domains using seed lists to identify issues before they impact real campaigns.
Regularly review your DMARC reports for insights into authentication failures and potential spoofing attempts.
Expert view
Expert from Email Geeks says: Microsoft SNDS seems to be experiencing issues this morning, indicating potential service disruptions affecting many users.
2023-10-18 - Email Geeks
Marketer view
Marketer from Email Geeks says: There was unexpected blocking on an IP listed as green with zero spam traps, despite SNDS showing good stats, highlighting data discrepancies.
2023-10-18 - Email Geeks
Navigating SNDS challenges for better deliverability
While Microsoft SNDS is an essential tool for monitoring email deliverability to Outlook.com, it comes with its own set of common issues. From frustrating access and data delays to misleading "green" statuses, senders must adopt a comprehensive approach to ensure their emails reach the inbox.
The key to overcoming these challenges lies in not solely relying on SNDS but combining its insights with other deliverability data, robust authentication practices, proactive list management, and continuous monitoring. A multi-faceted strategy is crucial for maintaining a strong sender reputation and achieving consistent inbox placement.
By understanding the limitations of SNDS and implementing broader email best practices, you can effectively troubleshoot issues and ensure your email program remains healthy and performs optimally for Microsoft recipients.
Outlook.com users. It offers data on spam complaints, junk mail reporting program (JMRP) feedback, and IP blocklist status, all crucial for maintaining healthy email sending. However, accessing and interpreting this data is not always straightforward, and senders often encounter common issues that can hinder their deliverability efforts.
Microsoft's end. Without real-time or even consistently fresh data, it's difficult to react quickly to deliverability issues, leaving email programs vulnerable to prolonged inboxing problems. This lack of transparency can be particularly frustrating during critical sending periods.
