Why does SNDS show 'normal status' but my emails are still being blocked?

SNDS primarily reports on IP and domain reputation, but email blocks can also stem from factors like content filtering, sudden volume spikes, poor list quality (e.g., hitting spam traps), or high user complaints that don't always reflect in the SNDS dashboard status. Even with a green status, your messages might be caught by other filters.

How can I identify the specific reason for Microsoft email blocks if SNDS isn't providing details?

Access your Email Service Provider's (ESP) logs or your mail server logs to find the exact bounce messages. These messages often contain specific error codes (like S3150) that indicate the reason for the block, providing crucial information for troubleshooting and contacting Microsoft support. Without these, it is very difficult to pinpoint the problem.

What is the best way to contact Microsoft support for email block issues?

You should use the Microsoft delisting form . Provide detailed information, including bounce messages, the IPs affected, and an explanation of your sending practices. Be prepared to be persistent, as initial responses may be automated. If you're managing Microsoft 365 for business, check the admin center for specific troubleshooting tools.

How do list quality and acquisition channels impact deliverability to Microsoft domains?

An increase in unengaged or fake email addresses can significantly hurt your sender reputation, leading to blocks. This is especially true if leads come from paid acquisition channels where users might enter invalid addresses. Microsoft heavily penalizes sending to addresses that generate high bounce rates or spam complaints.

What steps can I take to improve my email list quality and avoid future blocks?

You can implement practices such as requiring double opt-in for new subscribers, using email validation services at the point of data collection, and making email optional for certain user actions if poor data quality is a consistent problem. Regularly cleaning your email lists of inactive or bounced addresses is also crucial.

How to resolve Microsoft email blocks when SNDS shows normal status? - Troubleshooting - Email deliverability - Knowledge base

It can be incredibly frustrating when you're facing email delivery issues to

Microsoft domains, yet Microsoft's Smart Network Data Services (SNDS) indicates a normal or green status for your IP addresses. You're seeing emails bounced or simply not delivered to Outlook.com, Hotmail.com, and other Microsoft properties, but SNDS offers no clear explanation. This common scenario can leave you feeling stuck, wondering how to proceed when your primary diagnostic tool gives you a misleading all-clear signal.

The discrepancy between a normal SNDS status and actual email blocks points to a more nuanced deliverability challenge. While SNDS provides valuable insights into your IP and domain reputation with Microsoft, it doesn't always capture every factor influencing inbox placement. There are many layers to how mailbox providers filter incoming mail, and a green light on one indicator doesn't necessarily mean smooth sailing everywhere else. I'll walk you through why this happens and what steps you can take to diagnose and resolve these elusive email blocks.

Understanding this challenge is crucial for maintaining consistent email deliverability, especially when you're relying on email for critical transactional messages or marketing campaigns. The good news is that these blocks, while frustrating, are often addressable with a targeted approach to investigation and remediation.

Investigating beyond SNDS

It's a common misconception that a green SNDS status guarantees inbox delivery. While SNDS is a powerful tool for monitoring your email reputation with Microsoft, it primarily reflects IP-level reputation. Email blocking can occur for various reasons that aren't always immediately visible in the SNDS dashboard. This includes issues related to domain reputation, content filtering, recipient engagement, or even specific user complaints that trigger more localized blocks (blacklisting) that don't escalate to an IP-wide blocklist visible in SNDS.

The first step in diagnosing this issue is to look beyond SNDS and retrieve the exact bounce messages you're receiving. These messages often contain specific error codes or explanations (like S3150) that provide critical clues about why your emails are being blocked. Without these precise error messages, you're essentially trying to solve a puzzle without all the pieces. Your Email Service Provider (ESP) should be able to provide these logs. If you're using an internal mail server, you'll need to check your mail logs for delivery failures specifically to Microsoft domains like outlook.com, hotmail.com, and msn.com.

Once you have the bounce messages, you can use them as leverage when communicating with Microsoft. It's not uncommon for their initial responses to be boilerplate or automated, stating they can't find issues on their side. You'll need to be persistent. Reply to their emails, restate your problem clearly, include the specific error messages, and politely request an escalation. This often prompts a human review of your situation. You can find general guidance on deliverability issues with Hotmail (now part of Outlook.com) on the SNDS FAQ page. Additionally, for Microsoft 365 for business admins, there are tools to troubleshoot email delivery.

Common causes for hidden blocks

Even with a normal SNDS status, a sudden increase in email volume can trigger a block. Microsoft is sensitive to unexpected spikes, especially if your historical volume has been low. If your volume doubles overnight, it can resemble spamming behavior, leading to a temporary (or even prolonged) blocklist addition. This is particularly true if the volume increase is driven by new, potentially lower-quality leads, such as those from paid acquisition channels.

Another critical area to examine is your list quality and how email addresses are collected. If your acquisition channels, such as Facebook ads or Google keywords, are inadvertently leading to fake or poorly engaged email addresses, this can severely impact your sender reputation. Even if users are technically providing their own email, if they're entering addresses that aren't theirs, or if they're disengaged and prone to marking messages as spam, your sender reputation will suffer. Microsoft is very protective of its users' inboxes.

Consider implementing strategies to ensure email address validity at the point of collection. This could involve requiring email verification, using a double opt-in process, or even making email optional for certain actions if the data quality from mandatory collection is consistently poor. While it might be an internal battle, making email optional could drastically reduce issues from invalid or spam-trap addresses. You can also explore options to resolve email blocking issues with Microsoft domains by ensuring your data collection practices align with best deliverability standards.

Strategic adjustments and reputation management

When SNDS shows a normal status but you're still experiencing blocks, it's often a sign that the issue isn't a broad IP blacklist but rather a nuanced problem with your sending practices. Here's a comparative look at common issues and their solutions:

The problem

Volume spikes: Sudden, large increases in email volume can appear suspicious to Microsoft, even from a clean IP.
Poor list quality: Sending to invalid, old, or disengaged email addresses. This can trigger spam traps (a specific kind of blocklist) and high complaint rates.
Engagement issues: Low open rates, high bounce rates, and high spam complaint rates contribute to poor sender reputation, regardless of SNDS status.
Content flags: Email content that resembles spam or contains problematic links can be filtered, even from a good IP.

The solution

Gradual volume increase: Implement a proper IP warming strategy. Avoid sudden spikes in sending volume.
Strong list hygiene: Regularly clean your email lists. Implement double opt-in to ensure subscribers genuinely want your emails. Understand what spam traps are and how to avoid them.
Monitor engagement: Pay attention to your open and click rates, and especially monitor spam complaints through tools like Microsoft's Junk Mail Reporting Program (JMRP).
Content optimization: Ensure your email content is relevant, engaging, and avoids characteristics often associated with spam (e.g., excessive exclamation points, suspicious links, all caps). Review your email deliverability strategy.

For dedicated IPs, an increase in volume from a new or paid media acquisition channel can be particularly risky. While you might have internal checks for real users, people often provide fake email addresses to get access to services, which can result in hitting spam traps or generating complaints from legitimate users who didn't explicitly opt-in to your communications. This contributes to a poor sender reputation with Microsoft, even if SNDS appears normal. It's a subtle but significant factor in deliverability. For more insights on this, you can look into how to troubleshoot Microsoft email deliverability issues.

Proactive steps and continuous monitoring

Actionable next steps

If you're still experiencing blocks despite a normal SNDS status, it's time to get proactive with Microsoft support. Fill out their delisting form, providing all the details, including bounce messages and an explanation of your sending practices and any recent volume changes. Be polite but persistent. You may need to reply multiple times to boilerplate responses to get your issue escalated to a human agent. This process is crucial, as their automated systems may not fully grasp the nuance of a normal SNDS status combined with active blocks. For specific guidance, you can review what to do when Microsoft's SNDS IP review auto-reply is received.

If your sending volume fluctuates significantly, especially for transactional emails driven by paid media, consider strategies to smooth out these peaks. Implementing email verification at the point of lead acquisition or using double opt-in can help ensure that only valid and engaged email addresses receive your mail. This will drastically reduce the number of invalid addresses and potential spam complaints, which are major factors in Microsoft's filtering decisions. Remember, consistent positive engagement builds long-term sender trust, which is far more influential than a static SNDS status.

It's also beneficial to regularly monitor your email reputation across various blocklists (blacklists). While SNDS may show green, other less public blocklists could still be impacting your deliverability. Regularly checking your IPs against a comprehensive set of DNSBLs (DNS Blocklists) can provide an early warning system for potential issues not captured by Microsoft's own system. This multi-faceted monitoring approach is key to proactive deliverability management. You can learn more about this by reading our guide, an in-depth guide to email blocklists.

Final thoughts on deliverability

Achieving consistent email deliverability to Microsoft domains when SNDS shows normal status requires a holistic approach. It's about understanding that SNDS is one piece of a larger puzzle and that factors like list quality, send volume patterns, and recipient engagement play equally vital roles in whether your emails reach the inbox or hit a hidden blocklist (or blacklist). Prioritizing clean lists, managing volume carefully, and persistently engaging with Microsoft support are key to overcoming these challenges and ensuring your messages get through.

By combining external troubleshooting with diligent internal practices, you can improve your chances of reaching the inbox and maintain a healthy sender reputation, even when the immediate indicators seem contradictory. Remember, email deliverability is an ongoing effort that requires continuous monitoring and adaptation to mailbox provider policies and user behavior.

Views from the trenches

Best practices

Always retrieve and analyze bounce messages for specific error codes.

Implement double opt-in to verify subscriber consent and reduce spam complaints.

Carefully manage email volume spikes, especially for new acquisition channels.

Consistently monitor engagement metrics like open rates and spam complaints.

Common pitfalls

Assuming a normal SNDS status means no deliverability issues.

Ignoring bounce messages or not having access to detailed logs.

Failing to clean email lists regularly, leading to high bounce rates and spam traps.

Sending to unengaged or potentially fake email addresses from paid media.

Expert tips

Use email validation at the point of collection to prevent fake addresses.

Consider making email optional if quality issues persist from mandatory collection.

Bundle the cost of deliverability issues into your acquisition channel ROI.

Proactively monitor other blocklists, not just SNDS, for early warnings.

Expert view

Expert from Email Geeks says that a normal SNDS status does not guarantee 100% inbox placement.

October 29, 2019 - Email Geeks

Expert view

Expert from Email Geeks says that if you don’t get a clear answer from Microsoft, reply and restate your needs, asking for an escalation to a different person.

October 29, 2019 - Email Geeks