Why is SNDS data reporting inconsistent volume for senders?
Michael Ko
Co-founder & CEO, Suped
Published 12 Jun 2025
Updated 19 Aug 2025
7 min read
Microsoft's Smart Network Data Services (SNDS) is an essential tool for monitoring email deliverability to Microsoft recipients. It provides data on various metrics, including volume, complaints, and blocklist (or blacklist) status. However, a common issue many senders encounter is inconsistent volume reporting within SNDS. You might be sending millions of emails daily, yet SNDS only shows data for a handful of days each month.
This discrepancy can be perplexing and lead to misinterpretations of your email program's performance. It raises questions about the reliability of the data and whether your efforts to maintain a strong sender reputation are truly being reflected. Understanding why this happens is crucial for effective email program management and for troubleshooting potential deliverability problems.
My goal here is to shed light on why SNDS data can appear inconsistent regarding sending volume and what steps you can take to better interpret the information it provides. This includes delving into SNDS volume requirements and other factors that influence its reporting.
Understanding SNDS volume reporting
SNDS is designed to give high-volume senders insights into their email traffic, but it has specific thresholds. If your sending volume to Microsoft properties (like Outlook.com or Hotmail) falls below a certain daily message count, your data might not be displayed. Microsoft's FAQ states that reporting data should populate if more than 100 messages are sent from an IP to their systems. While this threshold is generally known, actual data visibility can sometimes require higher volumes.
Even if you are sending large volumes, the data in SNDS isn't real-time and often has a delay. This means you might be looking at data that is several hours or even a day old, which can create the illusion of inconsistency if you're checking frequently against live sending logs. Understanding the typical delay in SNDS data is important to avoid drawing premature conclusions.
Another factor is how SNDS aggregates data. It provides insights at the IP address level, not necessarily per individual sender or domain, especially if you're on a shared IP address. If multiple senders use the same IP, their combined volume might meet the threshold for data display, but the individual sender might not see their specific volume clearly represented.
Why volume inconsistencies occur
Several factors can contribute to SNDS reporting inconsistent volumes, even for senders with high daily traffic. These often relate to the nature of Microsoft's filtering mechanisms and how email is processed before data is collected.
Filtering and blocking: If a significant portion of your mail is being filtered, rate-limited, or outright blocked before it reaches Microsoft's internal systems that feed SNDS, that volume simply won't be recorded. This can happen if your IP is on a public or private blacklist (blocklist) or if your sending practices trigger their spam filters.
IP reputation and history: IPs with a poor historical reputation, even if they haven't sent mail recently, can be pre-emptively throttled or blocked. SNDS might show limited data for such IPs, even if you are sending significant volume.
Sending patterns: Inconsistent sending volume (e.g., sudden spikes or drops) can be flagged as unusual activity and impact how your mail is accepted and, consequently, reported in SNDS. Consistent volume builds trust with internet service providers (ISPs).
Low volume scenario
You send 50 emails to Microsoft recipients per day. This is below the general 100-message threshold. SNDS might show no data or very sporadic data, making it seem like you're not sending anything, even if these emails are being delivered.
High volume with issues
You send 1 million emails daily. However, due to a sudden increase in spam complaints or a blocklisting, Microsoft is rate-limiting your mail. SNDS might report significantly lower volume or missing days because a large portion of your mail isn't reaching the point where it's counted for reputation metrics. This can lead to SNDS data not displaying correctly.
It's also worth noting that SNDS data can be influenced by internal Microsoft system issues or maintenance. While less common, these could temporarily impact data reporting consistency. Always consider if there have been any announcements from Microsoft regarding SNDS availability or data issues.
Interpreting inconsistent data
When you observe inconsistent volume reporting in SNDS, it's natural to question the accuracy of your overall deliverability data. It's important to remember that SNDS is just one piece of the puzzle. While it provides valuable insights into your relationship with Microsoft, it doesn't always paint a complete picture of overall email deliverability.
If your internal sending logs show consistent high volume to Microsoft domains and you're seeing good inbox placement, opens, and clicks, then the SNDS volume inconsistency might simply be a reporting quirk or a sign that a portion of your mail is being silently filtered. This doesn't necessarily mean your emails are going to spam, but it does warrant further investigation.
How to approach the data
Cross-reference: Always compare SNDS data with your internal sending logs and other reputation tools (like Google Postmaster Tools for Google data) to get a holistic view of your sender reputation and deliverability.
Focus on key metrics: While volume is important, pay close attention to complaint rates, spam trap hits, and IP status. These indicators often provide more direct clues about your reputation than just volume data alone, especially if volume is inconsistent.
Inconsistent volume reporting in SNDS is a common phenomenon that can often be attributed to thresholds, data delays, and Microsoft's internal filtering. It doesn't always indicate a major deliverability problem, especially if other metrics are positive.
Best practices for using SNDS data
Despite occasional inconsistencies, SNDS remains a valuable resource for senders targeting Microsoft domains. To make the most of it and minimize confusion from volume discrepancies, consider these best practices.
First, ensure that your sending infrastructure is properly configured and that you are adhering to Outlook's sender requirements. This includes having valid SPF, DKIM, and DMARC records properly set up. Authentication plays a significant role in how ISPs view and process your mail, influencing whether your volume is even considered for reputation metrics.
Additionally, maintain consistent sending practices. Avoid sudden, drastic changes in volume without proper warming up of new IPs or domains. This helps build a stable reputation that ISPs can trust, leading to more reliable data reporting in SNDS and better overall inbox placement.
Views from the trenches
Best practices
Maintain consistent sending volumes to avoid triggering spam filters and ensure data stability in SNDS.
Regularly check your internal logs to confirm the actual volume of emails sent to Microsoft domains.
Ensure SPF, DKIM, and DMARC are correctly configured and aligned for proper email authentication.
Monitor other key deliverability metrics like complaint rates and spam trap hits in SNDS for a complete picture.
Common pitfalls
Assuming SNDS data is real-time or completely comprehensive for all sending scenarios.
Panicking over missing volume data without checking actual delivery rates or other reputation metrics.
Ignoring a poor IP history, as it can affect how Microsoft processes and reports your current sending.
Failing to meet the minimum volume thresholds, leading to no data being reported in SNDS.
Expert tips
For low-volume senders, focus more on content quality and engagement rather than solely relying on SNDS volume data.
If your IP was previously used by a less reputable sender, it might take longer for SNDS to reflect consistent, positive sending.
Discrepancies can sometimes be due to Microsoft's internal processing of mail, not necessarily an issue with your sending.
Remember that SNDS is a diagnostic tool, not a guarantee of inboxing, and should be used in conjunction with other data.
Marketer view
Marketer from Email Geeks says they rarely look at SNDS, and they only get data for maybe 4-8 days out of the month, even when their clients are sending daily.
2022-04-21 - Email Geeks
Marketer view
Marketer from Email Geeks says they see about the same data for their IP, but they only send weekly and at a low volume.
2022-04-21 - Email Geeks
Summary of findings
Inconsistent volume reporting in Microsoft SNDS is a common challenge for email senders. While it can be frustrating, it doesn't always signal a critical deliverability problem. Often, it's a reflection of minimum volume thresholds, data delays, or internal filtering processes by Microsoft.
The key is to use SNDS as one of several data points, cross-referencing it with your internal metrics and other deliverability tools. By understanding its limitations and focusing on the broader picture of your email program's health, you can make more informed decisions and maintain a strong sender reputation.
Ultimately, consistent good sending practices, including proper authentication, list hygiene, and engagement, will have the most significant impact on your email deliverability, regardless of minor fluctuations in SNDS volume reporting.
