Why are emails being filtered by Microsoft and ending up in junk folders?

Key findings

• Dynamic filters: Microsoft's filters are highly dynamic and adaptive, reacting quickly to changes in sending patterns and user feedback. This means what works one day might not the next.
• Reputation focus: Sender reputation, encompassing IP and domain reputation, is a primary factor. A poor reputation can lead directly to junk folder placement. Understanding email domain reputation is crucial.
• Authentication: Proper implementation of email authentication protocols like SPF, DKIM, and DMARC is fundamental. Microsoft heavily relies on these to verify sender legitimacy and combat spoofing. Learn about DMARC, SPF, and DKIM.
• Engagement metrics: High complaint rates, low open rates, and frequent deletions without opening can signal disengagement or unwanted mail, leading to filtering.
• Content analysis: Spam filters analyze email content for suspicious patterns, keywords, or formatting that might indicate spam. Understanding why emails end up in junk folders is important.

Key considerations

• Proactive monitoring: Continuously monitor your sender reputation and deliverability rates specifically for Microsoft domains.
• Audience segmentation: Send highly targeted and relevant content to engaged recipients to improve engagement metrics and avoid spam complaints.
• List hygiene: Regularly clean your email lists to remove inactive users, bounces, and potential spam traps.
• Feedback loops: Sign up for and actively use Microsoft's Sender Information for Outlook.com Postmaster tools (Junk Mail Reporting Program and Smart Network Data Services) to gain insights into your sending reputation and address issues promptly.

Key opinions

• Increased filtering: Many marketers have noticed an uptick in Microsoft's filtering issues, not just for Office 365, but across their services.
• Dedicated IP impact: A notable concern is the impact on dedicated IPs, with some marketers reporting that even clean clients using dedicated IPs see their traffic being junked. This is especially relevant during periods like IP warmup.
• Inconsistent delivery: There are reports of inconsistent delivery where identical messages sent from shared IPs might land in the inbox for some and junk for others.
• Recent shifts: Some marketers pinpoint specific dates, like mid-November, when these filtering changes seemed to intensify, possibly related to high-volume sending periods like Black Friday.
• Spam Confidence Level (SCL): A key factor for why emails end up in junk is Microsoft's SCL, which assigns a score to incoming messages, impacting their destination.

Key considerations

• Collaboration: Marketers find value in sharing observations to collectively understand and adapt to Microsoft's evolving filtering. This includes discussing Microsoft's email filters.
• Impact of events: High-volume sending periods, such as holiday sales, can correlate with increased filtering, suggesting that volume spikes might be a trigger.
• Segmentation refining: For lists with varying levels of activity, marketers should consider stricter segmentation to target only highly engaged recipients with critical communications.

Key opinions

• Reputation is paramount: Experts stress that maintaining a strong sender reputation is the single most important factor. This involves consistent, legitimate sending practices.
• Engagement signals: Beyond technical compliance, user engagement (opens, clicks, replies) and lack of negative feedback (complaints, deletions) heavily influence Microsoft's filtering. Poor engagement can lead to a high BCL score.
• Authentication standards: Properly configured SPF, DKIM, and DMARC records are non-negotiable foundations for deliverability to Microsoft. See technical solutions from top senders.
• Spam traps: Hitting Microsoft's spam traps can severely damage your sender reputation and result in immediate junking or blocklisting. Understanding how spam traps work is key.
• Content best practices: Experts recommend avoiding spammy content, excessive images, or links to questionable domains. Prioritize clear, concise, and relevant messaging.

Key considerations

• Audience re-engagement: Periodically re-engage less active segments or remove them to maintain a healthy list that positively influences your sending reputation.
• Monitoring Postmaster Tools: Utilize Microsoft's Postmaster Tools to gain insights into your sending performance and address any emerging issues directly.
• IP warming: For new IPs or significant volume increases, follow proper IP warming procedures to gradually build trust with Microsoft's filters.
• Proactive remediation: Address any deliverability issues quickly. Delays can worsen reputation problems and prolong junking.

Key findings

• Spam Confidence Level (SCL): Microsoft assigns an SCL to every inbound message, a numeric score indicating the likelihood of it being spam. Higher SCL values often mean the email is moved to junk or quarantine.
• Bulk Complaint Level (BCL): The BCL helps Microsoft identify bulk mail that is likely to generate complaints based on past recipient feedback. A high BCL indicates a problem with unwanted bulk mail.
• Authentication requirements: Microsoft's documentation strongly recommends and increasingly requires strong email authentication, including SPF, DKIM, and DMARC, to verify sender identity. Non-compliance can lead to junking or outright rejection. Understanding Outlook's new sender requirements is critical.
• User interaction: User actions, such as marking an email as 'junk' or adding a sender to the 'safe senders' list, directly influence how future emails from that sender are handled for that user and potentially for the wider network.
• Sender reputation: Microsoft's systems constantly evaluate sender reputation based on various signals, including volume, complaints, spam trap hits, and authentication pass rates. A poor reputation means emails are more likely to be filtered.

Key considerations

• Comply with guidelines: Adhere strictly to Microsoft's published sender guidelines and best practices to ensure optimal deliverability. Check Microsoft 365 Copilot junk email management.
• Monitor Postmaster Tools: Regularly review data from Microsoft's Postmaster tools, such as the Smart Network Data Services (SNDS) and Junk Mail Reporting Program (JMRP), for insights into your sending reputation and potential issues.
• Implement DMARC: Implement a DMARC policy (even at p=none) to gain visibility into your email ecosystem and detect unauthorized use of your domain.