Summary
Microsoft SNDS data often appears contradictory to actual email deliverability during IP warming due to several key factors. Primarily, SNDS is a lagging indicator, updating only daily, which means it cannot reflect the rapid, real-time changes in reputation that occur during the initial warming phases. Furthermore, SNDS provides an incomplete picture, focusing on aggregate data and acceptance rather than granular inbox placement, and it does not account for all internal factors Microsoft uses, such as user engagement or content quality. New IP addresses are often met with initial suspicion, leading to negative SNDS data even when emails are technically delivered to the junk folder, or filtering may occur silently without explicit bounces. The low sending volumes during early warming can also statistically skew complaint rates in SNDS, making the data seem worse than actual deliverability suggests. Additionally, the filter colors within SNDS can be misleading, as favorable colors may still coincide with significant spam placement.
Key findings
- Data Latency: Microsoft SNDS data updates only once every 24 hours, making it a lagging indicator that often fails to reflect the immediate, rapid changes in sender reputation that occur during IP warming phases.
- Limited Visibility: SNDS primarily reports on mail acceptance and aggregate data points, not comprehensive inbox placement. It does not fully capture all internal factors Microsoft uses for filtering, such as user engagement, content quality, or specific granular sending patterns.
- Initial IP Suspicion: New IP addresses are often treated with suspicion by Microsoft's filters. This can lead to initially high complaint rates or emails being routed to the junk folder, even if technically 'delivered,' causing SNDS data to appear negative as the system learns about the new IP.
- Low Volume Data Skew: During the initial low-volume stages of IP warming, even a small number of complaints can disproportionately impact the SNDS complaint rate, creating a misleadingly negative perception of reputation compared to actual deliverability.
- Misleading Filter Colors: The color-coded reputation signals within SNDS can be unreliable and misleading during the dynamic warming process, often showing favorable colors even when a high percentage of emails are placed in the spam folder.
Key considerations
- Diversify Monitoring: Do not rely solely on Microsoft SNDS data; supplement it with other indicators like certification data, seed lists, and real-time engagement metrics such as open and click rates to gain a comprehensive view of deliverability.
- Proactive Communication: Consider proactively contacting the Microsoft team before IP warming to inform them of anticipated volume and mail practices. This can help ease filtering, and senders can use the standard webform for this purpose, as there is no extra benefit from an ESP contacting on your behalf.
- Understand Filtering Paths: Be aware that Microsoft's filtering processes are complex, involving various escalation paths from mail being moved to the bulk folder, silent dropping, and different levels of rate limiting, to eventual IP and router blocking.
- Contextualize SNDS Data: Recognize that even favorable SNDS colors can co-exist with high spam placement during IP warming, and negative SNDS data in the initial stages is common and normal as Microsoft's filters learn about a new IP.
What email marketers say
15 marketer opinions
Microsoft SNDS data often presents a misleading picture during IP warming phases because it functions more as a lagging indicator rather than a real-time gauge of deliverability. While SNDS may report mail acceptance, this doesn't guarantee inbox placement, as Microsoft's complex, 'black box' internal filtering algorithms consider many factors beyond what SNDS exposes, including user engagement and content quality. These unmeasured signals can lead to significant spam folder placement or even 'silent mode' filtering-where emails are blocked without explicit bounces or notifications-even when SNDS shows favorable colors. Additionally, the low sending volumes typical of initial IP warming can statistically amplify the impact of even minor issues, causing SNDS complaint rates to appear disproportionately high compared to actual inboxing, further contributing to the perceived contradiction.
Key opinions
- Latent Reporting: SNDS data updates daily, functioning as a lagging indicator that cannot reflect the rapid, real-time shifts in sender reputation occurring throughout the dynamic IP warming process.
- Partial Insight into Placement: SNDS primarily reports on mail acceptance rather than granular inbox placement, often failing to indicate when emails are being routed to the spam folder despite appearing 'accepted' by Microsoft's systems.
- Opaque Filtering Factors: Microsoft's internal filtering algorithms operate as a complex 'black box,' incorporating numerous factors not visible in SNDS, such as user engagement metrics, content quality, and specific sending patterns, which can significantly influence deliverability.
- Silent Filtering Behavior: Microsoft may employ 'silent mode' filtering, where emails are blocked or dropped without explicit bounce notifications, resulting in 0% open rates, which can contradict seemingly benign SNDS data.
- Skewed Low Volume Data: During the initial low-volume phases of IP warming, even a minimal number of complaints can disproportionately inflate SNDS complaint rates, creating a misleadingly negative reputation signal.
- Deceptive Color Indicators: The color-coded reputation signals within SNDS can be misleading, as favorable or 'green' indicators may still coincide with a high percentage of emails being placed in recipients' spam folders.
Key considerations
- Holistic Deliverability Monitoring: To accurately assess IP warming progress, supplement SNDS data with a broader range of indicators, including real-time open and click rates, certification data, and seed list monitoring, as SNDS alone provides limited insight.
- Pre-Warming Outreach to Microsoft: Consider proactively contacting Microsoft's team via their standard webform before commencing IP warming to provide details on anticipated sending volumes and mail practices, which can help mitigate initial filtering challenges.
- Understand SNDS Limitations: Recognize that SNDS is a lagging and aggregate overview, not a real-time, granular deliverability report; interpret its data within the broader context of other performance metrics, especially during dynamic IP warming phases.
Marketer view
Marketer from Email Geeks explains that there is a difference between email acceptance and inbox placement, noting that during IP warming, senders can expect nearly 100% spam placement at Microsoft even if SNDS shows favorable colors. He clarifies that SNDS filter colors are useful but not the sole factor influencing placement decisions, suggesting other data sources like certification data or seeds are needed for increased visibility. He also states there is no extra benefit to having an ESP contact Microsoft for proactive mitigation compared to the sender doing it.
13 Apr 2024 - Email Geeks
Marketer view
Marketer from Email Geeks advises not to rely on Microsoft SNDS colors, suggesting they can be misleading.
11 Nov 2023 - Email Geeks
What the experts say
2 expert opinions
Microsoft SNDS data frequently presents a contradictory view of email deliverability during IP warming because its metrics do not fully capture the nuanced and often suspicious way Microsoft's filters treat new IP addresses. Expert insights indicate that SNDS colors are often unreliable, and poor SNDS data is a normal part of the warming process as Microsoft's systems learn about the new IP. Even if emails are 'delivered,' they may be routed to the junk folder, negatively impacting SNDS metrics. Furthermore, Microsoft employs a complex, multi-tiered filtering system, including silent dropping and various rate limits, which are not transparently reflected in SNDS, leading to a disconnect between reported data and actual inbox placement goals.
Key opinions
- Initial IP Suspicion: New IP addresses are frequently treated with suspicion by Microsoft's filters, which contributes to a perceived contradiction between SNDS data and actual deliverability during IP warming.
- Misleading SNDS Metrics: SNDS data can appear negative, showing high complaint rates or low 'successful delivery,' even when emails are not rejected but merely routed to the junk folder, as Microsoft's system is still learning about the new IP.
- Unreliable Color Indicators: Expert opinions highlight that the color-coded reputation indicators within SNDS are often unreliable and may not accurately represent the true state of deliverability or inbox placement.
- Silent Filtering Behavior: Microsoft's filtering includes 'silent dropping' of mail, where emails are discarded without explicit bounce notifications, a behavior that is not reflected in SNDS but significantly impacts overall deliverability.
- Complex Filtering Escalation: Microsoft utilizes a series of escalating filtering actions-from moving mail to the bulk folder and various forms of rate limiting to full IP and router blocking-which can explain discrepancies not visible in basic SNDS reporting.
Key considerations
- Anticipate Negative SNDS: Senders should expect and not be overly concerned by initially poor or negative SNDS data during the IP warming process, as this is a common and normal phase while Microsoft's filters learn to trust a new IP address.
- Interpret 'Delivery' Broadly: Understand that a low 'successful delivery' rate in SNDS might not indicate outright rejection, but rather emails being routed to the junk folder. This still impacts user engagement and perception, even if technically 'delivered'.
- Beyond SNDS Colors: Do not rely solely on the color-coded reputation signals in SNDS, as expert consensus indicates these can be unreliable and may not accurately reflect true inbox placement or Microsoft's internal filtering decisions.
- Awareness of Filtering Paths: Be aware of Microsoft's various filtering escalation paths, which include mail being moved to the bulk folder, silent dropping, different levels of rate limiting, and eventually IP or router blocking, all of which may not be transparently reflected in SNDS data.
Expert view
Expert from Email Geeks states that SNDS colors are unreliable and describes Microsoft's filtering escalation paths, which include mail being moved to the bulk folder, silent dropping (throwing mail on the floor), various levels of rate limiting, and finally IP blocking and router blocking.
23 Jul 2024 - Email Geeks
Expert view
Expert from Spam Resource explains that poor Microsoft SNDS data is common and normal during IP warming. New IP addresses are often treated with suspicion by Microsoft's filters, leading to initially high complaint rates or emails being routed to the junk folder, even if they are technically 'delivered'. SNDS data may appear negative because Microsoft's filtering is still learning about the new IP, and a low 'successful delivery' rate might reflect emails landing in the junk folder rather than being outright rejected, which can seem to contradict overall deliverability goals and the warming process.
28 Feb 2023 - Spam Resource
What the documentation says
3 technical articles
Microsoft SNDS data often contradicts observed email deliverability during IP warming due to its inherent operational characteristics. Documentation confirms that SNDS data updates only once every 24 hours, creating a significant delay in reflecting the rapid, real-time changes in sender reputation crucial for effective IP warming. Additionally, the dynamic nature of sender reputation, heavily influenced by mail volume and quality, means that the low sending volumes typical of initial warming phases might not supply sufficient data for SNDS to accurately or quickly capture the true, evolving reputation. Furthermore, SNDS provides aggregated daily data points, which means the granular, moment-by-moment fluctuations in deliverability during rapid reputation building are neither immediately visible nor precisely represented.
Key findings
- Data Update Delay: SNDS data updates only once daily, resulting in a significant delay in reflecting the real-time reputation changes essential for IP warming.
- Low Volume Data Insufficiency: Initial low-volume sending during IP warming might not generate enough data for SNDS to accurately or quickly portray the evolving sender reputation.
- Aggregate Data Lack of Granularity: SNDS primarily offers aggregated daily data, which fails to capture the granular, rapid fluctuations in deliverability experienced during the active reputation-building phase of IP warming.
Key considerations
- Account for Data Lag: Senders should be aware that SNDS data has a 24-hour update cycle, meaning it will always be behind real-time deliverability changes during IP warming.
- Understand Volume Impact: Recognize that low sending volumes in early IP warming stages can limit SNDS's ability to provide a complete and immediate picture of evolving sender reputation.
- Interpret Aggregate Data Carefully: Do not expect SNDS to provide granular, moment-by-moment insights; its aggregated daily data points may not reflect rapid deliverability shifts accurately.
Technical article
Documentation from Microsoft Learn explains that SNDS data is updated once every 24 hours, meaning there can be a delay in reflecting the most current reputation status during IP warming, which requires more real-time feedback.
13 Jun 2023 - Microsoft Learn
Technical article
Documentation from Microsoft Learn explains that sender reputation is dynamic and influenced by many factors, including the volume and quality of mail. This means low-volume sending during the initial phases of IP warming might not provide enough data for SNDS to accurately reflect the true, evolving reputation as quickly as deliverability changes.
6 Apr 2022 - Microsoft Learn
How accurate is Microsoft SNDS data for deliverability monitoring?
How to resolve Microsoft deliverability issues during IP warm up after being blocked?
Why are Microsoft email open rates low during IP warm-up?
Why are we seeing transactional deliverability issues on Microsoft even though SNDS seems to be showing up green?
Why do new IPs remain red in Microsoft SNDS during warming?
Why is Microsoft Outlook.com email deliverability inconsistent and how reliable is SNDS data?
