How to troubleshoot Microsoft emails going to spam after a template change?

Key findings

• Content sensitivity: Microsoft's filtering systems are highly sensitive to content changes. Even slight modifications in HTML, text, or image ratios can be perceived differently by their algorithms, leading to reclassification as spam.
• SCL impact: A template change can significantly alter the Spam Confidence Level (SCL) assigned by Microsoft. A higher SCL (e.g., SCL 6) indicates a higher likelihood of the email being junk, while a lower SCL (e.g., SCL 3) suggests it is more likely to reach the inbox. We have a dedicated guide on what email template changes affect Microsoft deliverability.
• Persistent issues: Reverting to an old, previously well-performing template may not immediately resolve the issue, suggesting that a reputation impact has occurred that requires time and consistent positive sending to mitigate.
• Varying delivery: It's not uncommon for identical emails sent from the same domain to experience different SCL scores and delivery outcomes across various Microsoft recipient addresses, indicating personalized filtering or cached reputation.
• Authentication role: The absence of robust email authentication, such as DMARC, can exacerbate content-related deliverability problems, as it deprives Microsoft of crucial trust signals. Learn how to troubleshoot and resolve Outlook email deliverability.

Key considerations

• Monitor SNDS: Regularly check Microsoft's Smart Network Data Services (SNDS) for changes in sender score, complaint rates, and SCL statistics. This provides insight into Microsoft's perception of your sending IP and domain.
• Analyze headers: Obtain and compare full email headers from before and after the template change. Look specifically for the X-Forefront-Antispam-Report section for clues about why the SCL might have changed.
• Implement DMARC: Ensure DMARC is properly configured. While not directly a content filter, it strengthens overall email authentication and trust signals, which can indirectly influence content-based filtering. Microsoft has also introduced new requirements for high-volume senders, which include strong authentication like DMARC. You can read more about Outlook's new requirements.
• Contact Microsoft support: If all self-service troubleshooting fails, open a ticket with Microsoft support. While initial responses may be automated, persistence can lead to human review and potential delisting or reputation adjustment.
• Holistic review: Beyond the template, assess other sending factors such as list quality, sending cadence, engagement metrics, and whether images are hosted on a well-reputed domain.

Key opinions

• Template sensitivity: Marketers commonly observe that changing an email template is often the sole variable when deliverability issues arise with Microsoft, even if other factors like list, cadence, and authentication domains remain constant. This is a common trigger for a drop in deliverability after content changes.
• SCL variability: It's noted that the same template, sent from the same domain, can receive different SCL scores (e.g., SCL 3 vs. SCL 6) for different Microsoft recipients, making it hard to pinpoint a consistent content-based trigger.
• Authentication role: While often a technical background task, marketers sometimes find themselves troubleshooting DMARC when content changes cause problems, suggesting an indirect link between content trust and authentication.
• Limited Microsoft support: Marketers express frustration with Microsoft's support, often receiving automated responses without clear explanations or immediate remediation.
• Persistent reputation impact: Marketers find that once Microsoft filters begin routing emails to spam, simply reverting to a known good template doesn't automatically restore reputation, indicating a need for a sustained positive sending strategy.

Key considerations

• Check all variables: Even if a template is the suspected cause, marketers should meticulously verify that no other factors, such as list changes, sending frequency, or changes in image hosting, have inadvertently occurred.
• Utilize SNDS: Microsoft's SNDS provides valuable data on deliverability, including SCL scores and complaint rates. Marketers are advised to compare headers from before and after the template change using SNDS to find clues.
• Assess content triggers: While difficult to pinpoint, consider elements in the new template that might trigger spam filters, such as excessive images, specific keywords, or unusual link structures. A general guide to running an email deliverability test can help.
• Engage Microsoft support: Despite challenges, opening and following up on support tickets with Microsoft is a necessary step for seeking remediation, especially when other avenues have been exhausted.
• Recipient instructions: As a short-term measure, advise recipients to check spam/junk folders and mark emails as not junk to help train filters. More tips on fixing deliverability issues for Outlook & Hotmail can be found here.

Key opinions

• Holistic filtering: Experts reiterate that Microsoft's filters assess both content and sender reputation (including IP and domain reputation), not just one in isolation. A new template might inadvertently trigger content filters, subsequently impacting the perceived reputation.
• Content as a trust signal: Changes in content can remove previously recognized patterns that Microsoft uses to identify legitimate mail from a specific sender. This can make the email appear 'new' or suspicious to the filtering algorithms.
• DMARC importance: Strong authentication, particularly DMARC, provides crucial signals to Microsoft and helps distinguish legitimate emails from potentially malicious ones. Its absence can make content-related issues harder to overcome. Learn more about DMARC, SPF, and DKIM.
• SNDS is critical: Utilizing Microsoft's SNDS program is essential for monitoring and diagnosing deliverability issues. It offers valuable insights into SCL, complaint rates, and IP/domain reputation.
• Hidden SPF DNS timeout: Microsoft's unique handling of SPF queries, including potential DNS timeouts, can lead to deliverability failures. This is a common but often overlooked factor affecting Microsoft deliverability, especially when content changes might expose underlying technical weaknesses. More information on why your emails fail at Microsoft.

Key considerations

• Beyond content: Experts advise looking beyond just the template to other factors that might have been indirectly affected or always weak, such as list hygiene, recipient engagement, and IP reputation. See our guide on sender reputation.
• Proactive DMARC: Implementing a DMARC policy (even at p=none initially) is a foundational step for all senders to gain visibility into email streams and improve trust signals with mail providers.
• Header deep dive: A thorough analysis of full email headers, particularly the X-Forefront-Antispam-Report details, can reveal specific reasons for spam placement and help identify problematic content elements or configurations.
• Microsoft communication: While challenging, persistence with Microsoft support and leveraging SNDS feedback loops is often necessary for resolving deliverability issues, as human intervention may be required.
• Reputation recovery: If a template change has negatively impacted sender reputation, a focused strategy including list cleaning, sending to engaged users, and maintaining consistent positive sending behavior will be required for recovery. Our guide on recovering email domain and IP reputation provides further details.

Key findings

• SCL explanation: Microsoft documentation details the Spam Confidence Level (SCL) as a score assigned to incoming messages, where a higher number indicates a greater likelihood of being spam. Changes in template content can influence this score.
• Content filters: Microsoft employs advanced content filters that analyze various aspects of an email's body, including text, HTML structure, images, and links, to identify characteristics of spam or phishing.
• SPF, DKIM, DMARC: Official guidelines strongly recommend implementing and properly configuring SPF, DKIM, and DMARC. These authentication standards are critical for verifying sender identity and preventing spoofing, thereby enhancing deliverability. A list of DMARC tags and their meanings can be a useful reference.
• SNDS insights: Microsoft's Smart Network Data Services (SNDS) provides senders with data on their IP reputation, spam complaint rates, and SCL statistics, which are essential for diagnosing and resolving deliverability issues.
• Sender requirements: Microsoft has published specific requirements for high-volume senders, which include maintaining low complaint rates, ensuring valid DNS records, and implementing robust authentication protocols. These are detailed in their strengthening email ecosystem announcement.

Key considerations

• Authentication compliance: Ensure all email authentication protocols (SPF, DKIM, DMARC) are correctly implemented and aligned. Microsoft specifically states that unauthenticated email is more likely to be filtered.
• Content best practices: Adhere to email content guidelines, avoiding characteristics commonly associated with spam, such as overly promotional language, suspicious links, broken HTML, or disproportionate image-to-text ratios.
• Monitoring tools: Leverage tools like Microsoft SNDS to proactively monitor sending reputation and diagnose issues related to IP and domain blacklisting or content filtering.
• Feedback loops: Register for and act upon complaint feedback loops (FBLs) to identify and remove disengaged recipients who mark your emails as spam. High complaint rates significantly degrade sender reputation.
• Recipient engagement: Microsoft, like other major mailbox providers, places increasing emphasis on recipient engagement. Low engagement or high deletes/junk reports for a new template can negatively impact future deliverability.