Why are SNDS and SFMC reports showing discrepancies in email delivery data, and how to resolve it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Jun 2025
Updated 19 Aug 2025
9 min read
It can be incredibly frustrating when the data you rely on to assess email delivery tells different stories. Specifically, when Microsoft's Sender Network Data Services (SNDS) and Salesforce Marketing Cloud (SFMC) reports show conflicting email delivery data, it creates a significant challenge for marketers and deliverability professionals. This often arises during critical periods, like IP warming, where accurate insights are crucial for building a solid sender reputation.
The core of the problem stems from the different vantage points each system has. SFMC reports on what happened from its end as an email service provider (ESP), indicating whether an email was successfully handed off to the recipient's mail server. SNDS, on the other hand, reports on how Microsoft's systems perceived and processed the incoming mail. When these two perspectives don't align, it leaves senders questioning the true status of their email campaigns.
I've encountered this issue countless times, and it's a common source of confusion for senders trying to maintain good email deliverability. The goal is always to get your emails to the inbox, but when your reporting tools conflict, it's difficult to identify what's truly happening and how to address it. Let's delve into why these discrepancies occur and how to resolve them.
Understanding SNDS and SFMC data
Understanding what each reporting tool measures is the first step in deciphering discrepancies. Microsoft SNDS (Smart Network Data Services) offers insights into the health of IPs sending to Microsoft properties, such as Hotmail, Outlook.com, and Live.com. It provides data points like RCPT (Recipients) and DATA (Message Recipients), indicating the volume of emails accepted and processed by Microsoft's servers. You can learn more about how to get SNDS and JMRP data for Salesforce/ExactTarget users to get a clearer picture.
Salesforce Marketing Cloud (SFMC) provides its own set of tracking and reporting metrics within its platform. These reports typically show metrics like delivered, bounced, opens, and clicks. The delivered status in SFMC signifies that the email was successfully accepted by the recipient's mail server. It doesn't necessarily guarantee inbox placement, only that the initial SMTP transaction was completed successfully.
A key distinction is that SFMC reports reflect the ESP's perspective, while SNDS provides insights directly from Microsoft's receiving servers. This difference in reporting scope is a fundamental reason for discrepancies. For example, SFMC might report 10,000 emails as delivered to Microsoft, but SNDS might show a significantly lower RCPT count. This usually indicates that while SFMC initiated the send, Microsoft either rejected a large portion of those emails at a deeper level or experienced a delay in processing, which isn't immediately visible in SFMC's initial report. You may find insights on this in Marketing Cloud Intelligence and Discover Reports.
Why discrepancies occur
Several factors contribute to the discrepancies between SNDS and SFMC data, making it challenging to get a unified view of your email deliverability. I've broken down the most common reasons I've observed:
Data processing delays: SNDS data can sometimes be delayed or even entirely missing for certain days, especially during periods of high volume or if Microsoft experiences system issues. Similarly, SFMC's internal data views may take time to update, leading to temporary mismatches.
Time zone differences: Depending on your sending time and your timezone relative to the recipient's mail server, a single day's send could be spread across two days in SNDS or SFMC reporting, causing skewed daily volumes. This is a common pitfall in SNDS data delays.
Deferred bounces and retries: SFMC might classify an email as delivered initially if Microsoft accepts it for deferred delivery, even if it eventually bounces. SFMC's last retry attempts can extend up to 72 hours, meaning a final bounce status might not appear until much later. Some 4xx bounces won't show up until then.
Silent drops: This is one of the most perplexing issues. Microsoft may accept an email at the SMTP level, leading SFMC to report it as delivered, but then silently drop it later due to content, recipient engagement, or IP reputation issues, without sending a bounce code back to SFMC. This results in a low DATA count in SNDS.
IP reputation and throttling: If your IP (or sending domain) reputation with Microsoft is low, they might temporarily rate-limit or block your emails. While SFMC might still attempt to send, SNDS would reflect the reduced acceptance. SNDS colors (red, yellow, green) give a general indication of this, but the raw data is key.
Resolving the data inconsistency
When facing these discrepancies, a systematic approach is necessary to pinpoint the root cause. Here's how I typically recommend investigating and working towards a resolution:
I often see confusion between RCPT and DATA in SNDS. The former refers to the total number of recipient addresses Microsoft received for the given IP, while the latter is the number of unique messages. Ideally, these numbers should be very close, with any significant difference indicating rejected emails at the SMTP level. If SFMC shows high delivery but SNDSRCPT and DATA counts are much lower, it signals a significant problem on the Microsoft side that SFMC's reporting isn't capturing as a bounce. This often points to silent drops (or silent blacklisting/blocklisting), where Microsoft accepts the email but then discards it without generating a bounce notification.
I always advise my clients to compare the delivery numbers in SFMC with the RCPT and DATA counts in SNDS. If there's a significant gap where SFMC indicates delivery but SNDS doesn't reflect the volume, it’s a red flag. You need to identify if emails are being deferred, blocked, or silently dropped. Check your SFMC Email Studio for bounce management and analyze the SMTP bounce reasons reported by SFMC. This is critical for understanding why Microsoft might be rejecting mail.
If you've checked all these areas and still see persistent discrepancies, especially with low DATA counts in SNDS despite SFMC reporting high delivery, it might indicate silent drops. This is a trickier scenario, as there's no explicit bounce message to guide you. In such cases, maintaining consistent sending volume is often recommended to give Microsoftdata to evaluate your sending reputation over time. However, simply waiting and hoping is rarely an effective strategy. Proactive engagement and meticulous data analysis are essential.
Investigating and troubleshooting
Addressing these discrepancies often requires digging deeper into the data and understanding the nuances of how each system processes and reports email delivery. Here's a table summarizing the key data points to compare:
Metric
SNDS (Microsoft's perspective)
SFMC (ESP's perspective)
RCPT (recipients)
Total recipient addresses Microsoft received attempts for.
Number of emails SFMC attempted to send to Microsoft domains.
DATA (message recipients)
Unique messages Microsoft accepted for delivery after SMTP handshake.
Not a direct equivalent. SFMC's 'delivered' count is the closest.
Bounces
Not explicitly reported as bounces. Lower DATA vs. RCPT indicates rejections.
Categorized as hard, soft, or technical bounces, with specific SMTP codes.
IP status/color
Visual indicator (red, yellow, green) of IP reputation with Microsoft.
Not directly available. Inferred from bounce rates and inbox placement.
In addition to direct data comparison, it's vital to communicate with SFMC support. They have access to deeper logs and telemetry that are not exposed through standard reporting tools. While they may be hesitant to comment directly on SNDS data, they can provide critical information on their side regarding SMTP transaction details, rate limits encountered, or any internal system issues that might be affecting delivery to Microsoft domains.
Best practices for data alignment
Regular reconciliation: Periodically compare SNDSRCPT and DATA metrics with SFMC's delivered counts to spot trends early.
Monitor SMTP logs: If available, review raw SMTP logs from SFMC to confirm email acceptance or rejections by Microsoft servers.
Maintain consistent sending: For IP warming or reputation recovery, consistent sending helps Microsoft (and other ISPs) build a reliable profile of your sending behavior. Don't stop sending, but adjust volume as needed.
Views from the trenches
Best practices
Always cross-reference your ESP's delivery reports with postmaster tools like SNDS to get a holistic view of email performance.
Understand the nuances of each reporting tool. SNDS is Microsoft's view, SFMC is your ESP's view. Both are valid but different.
If SNDS data is missing or very low, it could indicate silent drops, temporary blocks, or data processing delays on Microsoft's end.
Segment your audience for IP warming and gradually increase volume to specific domains like Microsoft to build reputation systematically.
Leverage SFMC's tracking data and SMTP bounce codes to identify specific reasons for non-delivery or high spam placement.
Common pitfalls
Assuming SFMC's 'delivered' count means inbox placement, when it only means acceptance by the receiving server.
Panicking over temporary SNDS data anomalies. Some delays are normal; wait 24-72 hours for data to stabilize.
Not engaging SFMC support when facing persistent, unexplainable discrepancies, as they have deeper access.
Reducing sending volume too drastically during IP warming or reputation issues, which can hinder the reputation-building process.
Ignoring low open rates at specific domains, as this can be an indicator of spam folder delivery even if emails show as 'delivered'.
Expert tips
For silent drops, focus on improving sender reputation through consistent engagement, list hygiene, and content quality.
Monitor IP and domain reputation regularly. Tools like SNDS can show if your IPs are getting blacklisted or blocklisted.
Ensure your email authentication (SPF, DKIM, DMARC) is correctly configured, as this significantly impacts deliverability.
Be patient during IP warming, it's a gradual process. Don't expect immediate green lights from all postmaster tools.
Utilize engagement metrics from SFMC to gauge actual inbox placement and recipient interaction, not just delivery counts.
Marketer view
Marketer from Email Geeks says sometimes SNDS data is missing entirely, and sending over two days from Microsoft's point of view can explain discrepancies.
2020-01-08 - Email Geeks
Marketer view
Marketer from Email Geeks says they should double-check SMTP logs to confirm all expected traffic went through the designated IPs.
2020-01-08 - Email Geeks
Navigating data discrepancies for better deliverability
Dealing with discrepancies between SNDS and SFMC delivery reports can be a significant hurdle for email marketers and deliverability professionals. It's crucial to remember that these tools offer different perspectives, and neither is inherently wrong, but they report on different stages of the email delivery process.
By understanding the potential causes of these inconsistencies, such as data delays, time zone differences, deferred bounces, and silent drops, you can adopt a more informed approach to troubleshooting. Always cross-reference data, engage with SFMC support, and focus on building a strong, consistent sender reputation. This proactive stance will enable you to navigate the complexities of email deliverability more effectively and ensure your messages reach their intended recipients.
Salesforce Marketing Cloud (SFMC) reports show conflicting email delivery data, it creates a significant challenge for marketers and deliverability professionals. This often arises during critical periods, like IP warming, where accurate insights are crucial for building a solid sender reputation.
Microsoft SNDS (Smart Network Data Services) offers insights into the health of IPs sending to Microsoft properties, such as Hotmail, Outlook.com, and Live.com. It provides data points like RCPT (Recipients) and DATA (Message Recipients), indicating the volume of emails accepted and processed by Microsoft's servers. You can learn more about how to get SNDS and JMRP data for Salesforce/ExactTarget users to get a clearer picture.
