Why is my Microsoft SNDS data not reflecting my actual deliverability issues?

SNDS often provides general reputation data and can be slow to update. It might show a "normal" status even when your emails are being filtered to spam. Focus on analyzing email headers for BCL/SCL scores and internal ESP metrics like spam complaints for more accurate insights into Microsoft Outlook.com deliverability .

How do I check BCL and SCL scores for my emails?

Send an email to a Microsoft inbox you control, then access the full message headers. Look for the X-Forefront-Antispam-Report header, which contains values for BCL (Bulk Complaint Level) and SCL (Spam Confidence Level). These scores directly indicate Microsoft's filtering assessment of your email.

Can low engagement with my emails affect Microsoft deliverability?

Yes, recipient engagement is a critical factor for Microsoft. Low open rates, ignored emails, and high spam complaints signal to Microsoft that your content isn't desired, which can negatively impact your sender reputation and lead to emails being filtered.

What role do SPF, DKIM, and DMARC play in Microsoft deliverability?

SPF, DKIM, and DMARC are essential email authentication protocols. They help Microsoft verify your email's legitimacy, preventing spoofing and ensuring proper alignment. Correctly configuring these records is fundamental to achieving good inbox placement. You can learn more in this guide to DMARC, SPF, and DKIM .

How can subdomains help with Microsoft deliverability issues?

Using subdomains allows you to separate the sending reputation of different email streams. For example, marketing emails can use one subdomain, and transactional emails another. This prevents issues with one stream (e.g., high spam complaints) from negatively impacting the deliverability of your other, more critical emails.

What should I do if my emails are still blocked despite good SNDS status?

If SNDS shows normal, but emails are blocked, it suggests underlying issues not captured by SNDS. Investigate email headers, review all Microsoft domains contributing to blocks , check your ESP's internal metrics (bounces, complaints), and ensure your DMARC policy is robust. Consider a comprehensive audit of your email program.

How to troubleshoot Microsoft email deliverability issues and analyze SNDS data? - Troubleshooting - Email deliverability - Knowledge base

Dealing with Microsoft email deliverability can often feel like navigating a complex maze. Many senders find their emails struggling to reach the inbox, even when all the standard authentication protocols like SPF, DKIM, and DMARC appear to be correctly configured and passing. I've seen firsthand how frustrating it can be when your deliverability monitoring tools show inconsistent results, or when engagement metrics begin to decline without a clear cause.

A common first step for many is to check Microsoft's Smart Network Data Services (SNDS), hoping for insights similar to what Google Postmaster Tools offers. However, it's often reported that SNDS can be less informative or even misleading, sometimes showing a normal status even when emails are not reaching the inbox. This article will guide you through effective troubleshooting strategies for Microsoft deliverability and how to interpret the data you do receive, including diving deeper than just SNDS.

I've compiled insights and practical steps to help you diagnose and resolve these elusive email delivery issues in Microsoft 365, focusing on what truly impacts your sender reputation and how to get your messages delivered. We'll explore methods beyond basic monitoring, ensuring your emails consistently land in the intended recipients' inboxes.

Analyzing Microsoft SNDS and email headers

While Microsoft SNDS is the official source for IP reputation data, its utility for real-time, granular troubleshooting is often debated. It provides a general overview, but can be slow to update and lacks the detailed insights needed for proactive problem-solving. It's not uncommon for senders to report that SNDS data can be inconsistent or misleading.

For more immediate and actionable insights, I recommend examining the email headers. These headers contain crucial information like the Bulk Complaint Level (BCL) and Spam Confidence Level (SCL) scores, which are assigned by Microsoft Exchange Online Protection (EOP). A high BCL indicates a significant number of recipients marking your emails as spam, while a high SCL suggests EOP considers your email spammy. Understanding these scores is often more beneficial than a green light in SNDS.

Checking email headers for BCL/SCL scores

You can find these scores by sending an email to a Microsoft inbox you control, then viewing the message headers. Look for X-Forefront-Antispam-Report header and dissect its contents.

Example of email header snippettext

X-Forefront-Antispam-Report: ...; BCL:0; SCL:1; ...

Engagement as a key driver for deliverability

One of the most impactful factors for Microsoft deliverability is recipient engagement. Microsoft, like other major mailbox providers, heavily monitors how subscribers interact with your emails. Declining open rates, even if less reliable than before, or an increase in spam complaints, will quickly signal to Microsoft that your mail is not valuable to their users. This can lead to your emails being filtered to the junk folder or even outright blocked (blacklisted or blocklisted, to use both terms).

I've seen situations where even authenticated senders with a seemingly clean SNDS record face issues due to low engagement. This is particularly true for B2B senders, where recipients might not frequently engage with marketing emails but still value transactional or important communications. It's a delicate balance, and sometimes transactional emails experience issues on Microsoft domains despite good sender metrics.

Poor list hygiene

Disengaged contacts: Sending to recipients who haven't opened or clicked in a long time lowers your engagement rates and signals to Microsoft that your content isn't relevant.
Purchased lists: These often contain spam traps and uninterested recipients, leading to blocklistings (blacklistings) and severe reputation damage.

Best practices for engagement

Segment and suppress: Regularly remove or suppress inactive subscribers. Consider re-engagement campaigns for those on the edge.
Permission-based lists: Always ensure your recipients have explicitly opted into receiving your emails. This is fundamental for good deliverability.

Proactively managing your list to remove disengaged contacts is crucial. While it might feel counterintuitive in a B2B context where long sales cycles are common, keeping highly disengaged users on your primary sending lists can negatively impact your overall sender reputation. Consider separate sending strategies or re-engagement flows for such contacts.

Authentication and infrastructure best practices

Email authentication protocols, including SPF, DKIM, and DMARC, are foundational for good deliverability, especially with Microsoft. These records prove that you are authorized to send emails from your domain and help prevent spoofing and phishing. Ensuring their correct implementation is non-negotiable.

Ensure proper authentication setup

SPF: Verify your SPF record includes all legitimate sending IP addresses and services. An SPF DNS timeout can cause unexpected failures at Microsoft.
DKIM: Ensure your DKIM signatures are correctly generated and published. Monitor for any DKIM temperror rates with Microsoft.
DMARC: Implement a DMARC policy. Starting with p=none allows you to monitor your email streams without impacting delivery. Suped offers the most generous free plan for DMARC monitoring and reporting, providing crucial insights into your email authentication.

When migrating ESPs or making significant changes to your email infrastructure, such as moving to new subdomains, a proper warm-up process is vital. Even if you've done this, changes can sometimes lead to unexpected fluctuations in deliverability. Subdomains can help isolate your reputation, preventing issues from one sending stream from affecting another. However, each new subdomain will build its own reputation, which takes time.

Sometimes, if internal employees are not adhering to best sending practices, it might even make sense to consider entirely separate sending infrastructures for different types of email traffic, like marketing vs. transactional emails. This is a more drastic step but can be necessary to protect your core email deliverability.

Beyond SNDS: Monitoring other vital metrics

While SNDS might not provide the granular detail you always want, it’s still part of the puzzle. Regularly checking the IP status dashboard can alert you to major issues. However, if SNDS shows normal status but you're still experiencing problems, it's time to dig into other metrics. This includes closely monitoring bounces, unsubscribe rates, and spam complaints within your ESP.

It's also important to remember that tools like SNDS and Google Postmaster Tools primarily provide data for consumer (B2C) mailstreams. For B2B senders, where recipient volume to any single mailbox provider like Outlook.com might be lower, their data may offer less actionable insights on specific paid customer domains.

Indicator	What to look for	Impact on deliverability
Bounce rate	High percentages of hard and soft bounces.	Indicates poor list quality, which can lead to blocklisting (or blacklisting) and degraded sender reputation.
Spam complaint rate	Any noticeable increase, especially to Microsoft domains.	The fastest way to land in the junk folder and get blocklisted. Seriously damages your reputation.
Unsubscribe rate	Elevated rates suggest content misalignment or frequency issues.	While not as severe as complaints, high unsubscribes still indicate disengagement and can hurt sender reputation over time.

I recommend continuous DMARC reporting and monitoring to catch authentication issues early, and leveraging internal data from your ESP to understand recipient behavior. Sometimes, fixing these issues requires a multi-pronged approach that goes beyond what any single postmaster tool can tell you.

Advanced troubleshooting and program review

Sometimes, despite all best efforts, your emails might still be struggling. This is when it's critical to conduct thorough testing and analysis. Performing seed list tests with various mailbox providers, including Microsoft, can highlight where issues are occurring. It's not uncommon to see inconsistent results even within seed lists, particularly with services like Gmail that make highly individualized delivery decisions.

If you are migrating between ESPs, ensure your DNS records for SPF and DKIM are updated correctly for the new sending platform. Sometimes, issues arise because old records conflict or new ones are not propagated properly. Even migrating only engaged users can present challenges if Microsoft perceives a sudden change in sending patterns.

For ongoing issues, it might be beneficial to review your entire email program. Look at audience segmentation, content relevance, sending frequency, and overall user experience. Sometimes, a subtle shift in any of these areas can trigger a decline in deliverability. Understanding the full picture, rather than focusing on a single metric, is key to sustained inbox placement.

Views from the trenches

Best practices

Actively suppress or remove disengaged contacts to maintain a healthy sender reputation and improve inbox placement.

Use subdomains to isolate the reputation of different email streams (e.g., marketing vs. transactional).

Regularly monitor BCL/SCL scores in email headers for immediate feedback on Microsoft filtering decisions.

Implement a robust DMARC policy (even at p=none) to gain visibility into your email authentication status.

Common pitfalls

Over-reliance on SNDS data alone, as it can be outdated or lack granular insights for active troubleshooting.

Sending to 'fresh new lists' without proper warming or verification, which often leads to spam traps and blocklistings.

Ignoring declining engagement metrics, as these are strong signals to mailbox providers about content relevance.

Not considering B2B vs. B2C data limitations in postmaster tools for paid customer domains.

Expert tips

If basic troubleshooting fails, analyze anti-spam message headers and SMTP logs for specific error messages.

Consider engaging a deliverability consultant for targeted and focused fixes if issues persist.

Benchmarking your own open rates month-over-month can still provide valuable insights into trends, despite their general unreliability.

Ensure all authentication (SPF, DKIM, DMARC) is correctly configured, especially after ESP migrations.

Expert view

Expert from Email Geeks says Microsoft free or paid inboxes can show different deliverability behavior, and examining BCL/SCL scores in email headers often provides more direct information than SNDS.

2025-04-29 - Email Geeks

Marketer view

Marketer from Email Geeks says engagement going down is a critical sign, and it's essential to proactively remove disengaged contacts to maintain a high sender reputation.

2025-04-29 - Email Geeks

Putting it all together for better deliverability

Troubleshooting Microsoft email deliverability requires a holistic approach, looking beyond a single tool like SNDS. While SNDS provides a baseline, granular data from email headers, diligent engagement monitoring, and robust authentication practices are far more crucial for maintaining strong email deliverability to Microsoft domains.

By understanding the limitations of certain tools and focusing on comprehensive list management, authentication verification, and consistent monitoring of your email programs, you can significantly improve your chances of reaching the inbox. If you encounter persistent issues, a deeper dive into your email logs or even seeking expert assistance might be the best course of action.