Why am I suddenly getting an influx of spam complaints?

Key findings

• Microsoft Exchange Online Protection (EOP) BCL Score: A high Bulk Complaint Level (BCL) score, such as 5, indicates that your email is perceived as bulk or spam by Microsoft's internal filtering system. While a higher score isn't always problematic, it can significantly impact deliverability to O365 users, potentially triggering complaints.
• BCL vs. Outlook/Hotmail: It's important to note that Outlook.com and Hotmail (consumer-grade services) do not directly use the BCL scores for their filtering decisions. Complaints from these domains suggest other factors are at play, although a negative sender reputation with Microsoft could still affect them broadly.
• Recipient Behavior Impact: The way recipients interact with your emails (or choose not to) heavily influences your sender reputation. Even if an email initially lands in the inbox, recipients marking it as spam can lead to immediate and future deliverability issues. This is often not captured by pre-send deliverability tests.
• Limited Value of Standard Deliverability Tests: Many public deliverability testing tools use open-source software and don't reflect the complex, dynamic algorithms used by major mailbox providers. Relying solely on these tests can provide a false sense of security.
• False Flags and Misinterpretations: What appears to be a direct cause, such as a BCL score, may not be the primary driver of complaints from all Microsoft domains. It might be a symptom of broader reputation issues or message content problems.

Key considerations

• Monitor Spam Complaints Directly: Focus on actual spam complaint feedback loops (FBLs) and data from tools like Google Postmaster Tools rather than relying on generalized deliverability scores.
• Content and Context Review: Even if subject lines previously performed well, a sudden shift in filtering could be due to subtle content changes, image use, or even external factors like a rise in related scams (e.g., tax-related scams during tax season).
• List Hygiene: While you may not be collecting illegitimate subscriptions, an old or unengaged list can suddenly begin to generate complaints. Ensure you have clear, permission-based opt-in processes.
• Investigate Link Domains: The domains used in your email links (including tracking links) can impact sender reputation. Ensure they are not on any blocklists or associated with problematic sending history. You can learn how to stop spam emails by addressing these underlying issues.
• Contextual Deliverability: Deliverability is highly contextual and depends on how individual mailboxes and their users react. What works one day might not the next due to shifts in user behavior or filtering algorithms.

Key opinions

• Unexpected Spikes are Puzzling: Marketers frequently express confusion when emails with previously good performance suddenly trigger a high volume of spam complaints, especially with consistent content and subject lines.
• Concerns over Microsoft Filtering: Microsoft Exchange Online Protection (EOP) and its Bulk Complaint Level (BCL) criteria are often cited as primary suspects when deliverability issues arise, even if the direct link to consumer mailboxes isn't always clear.
• Pre-delivery Classification: Observations suggest that many messages are classified as spam before users even have a chance to open or click them, leading to complaints that might not reflect direct user interaction.
• Seasonal and External Factors: External factors, such as an increase in phishing scams related to a specific topic (e.g., tax-related scams), can cause legitimate senders to be caught in broader filtering nets, even if they are a known sender.
• Reluctance to Blame List Quality: Marketers are often confident in their list acquisition methods (e.g., existing product users), making them less inclined to believe the problem stems from illegitimate subscriptions.

Key considerations

• Contextual Relevancy: While your content might be relevant to your audience, its resemblance to current scam trends (e.g., tax season scams) can inadvertently flag it. Understanding how to get less spam can inform your sending practices.
• Beyond Deliverability Tests: Marketers need to look beyond simplistic deliverability tests, which do not accurately reflect real-world spam filter complexities or recipient engagement.
• Monitoring Outlook/Hotmail Specifics: Despite no direct FBL for O365, a high proportion of complaints from Outlook/Hotmail indicates a need for deeper investigation into your standing with Microsoft, potentially by reviewing Outlook and Hotmail deliverability.
• Holistic View: A sudden jump in spam complaints might be preferable to a deeper, more systemic deliverability issue, as it could indicate a one-off campaign or content misstep. However, it still warrants careful observation.
• Track Spam Complaints: Implement systems to track spam complaints accurately to identify trends and specific campaigns causing issues.

Key opinions

• BCL is O365 Internal Only: The Bulk Complaint Level (BCL) score is an internal Microsoft metric specifically for O365 users, allowing O365 tenants to customize their filtering thresholds.
• No O365 FBL: Microsoft Office 365 (O365) does not provide a Feedback Loop (FBL) for spam complaints, meaning external systems cannot directly track user-initiated spam reports from O365 environments.
• Outlook/Hotmail Don't Use BCL: Consumer-facing Outlook.com and Hotmail services do not utilize BCL scores in their filtering decisions, indicating that complaints from these domains stem from other reputation or content factors.
• Deliverability Tests Are Misleading: Most widely available deliverability tests are based on open-source software and do not reflect the sophisticated, proprietary algorithms used by major spam filters. This means they often provide inaccurate or incomplete assessments.
• Recipient Reaction is Paramount: A significant portion of deliverability success depends directly on how recipients engage (or don't engage) with your emails. This dynamic feedback is crucial but often not measured by pre-send tests.
• Complexity of Modern Filters: Current spam filtering is far more intricate than older systems (like SpamAssassin) and involves complex, non-public methods that make simple 'tests' inadequate.

Key considerations

• Focus on Recipient Engagement: Prioritize strategies that encourage positive recipient interaction (opens, clicks, replies) and minimize negative actions (spam reports, deletions without reading). This is key to improve email deliverability.
• Don't Over-rely on Litmus/Spam Tests: Understand that these tools offer a limited view and should not be the sole basis for diagnosing deliverability issues. Consider using an email deliverability tester if it analyzes real-world inbox placement.
• Scrutinize Links and Domains: Perform thorough checks of all links within your email, including tracking domains, to ensure they are clean and not contributing to blacklisting. This helps prevent your emails from going to spam.
• Address Content-based Spam Triggers: If complaints are rising, review your email content, including images and wording, for anything that might inadvertently trigger spam filters, especially during periods of increased phishing activity.
• Microsoft Compliance: Ensure your sending practices align with Microsoft's sender requirements and best practices for deliverability, as they have specific guidelines for bulk mail.

Key findings

• BCL Score Definition: Microsoft's documentation defines BCL (Bulk Complaint Level) as an indicator of whether an email is likely to be bulk mail, with higher scores suggesting a greater likelihood of being perceived as spam by users.
• Score Interpretation: BCL values range from 0 (good, clean mail) to 9 (bad, spammy mail), with a score of 5 or higher indicating increasing suspicion as bulk mail that could be filtered or quarantined.
• Impact on EOP: In Exchange Online Protection (EOP), the BCL value contributes to the overall SCL (Spam Confidence Level) of an incoming message, which then determines its handling (e.g., delivered to inbox, junk folder, quarantined).
• Admin Control: EOP administrators can configure bulk complaint thresholds for their organization, choosing at which BCL score level bulk email should be treated as spam or junk.
• Purpose of BCL: The BCL helps EOP identify and filter legitimate bulk email that users might still complain about, even if it's not traditional spam, ensuring a better user experience within O365.

Key considerations

• Bulk Mail vs. Spam: Recognize that BCL primarily categorizes bulk mail, which may be legitimate but unwanted by recipients, rather than outright malicious spam. This distinction is critical for understanding complaint sources.
• Targeting O365 Recipients: If a significant portion of your audience uses O365, understanding and managing your BCL score is paramount to avoid being filtered based on tenant-specific configurations. This impacts how you comply with Outlook's new sender requirements.
• Content and List Hygiene for Bulk: To maintain a low BCL, focus on highly engaged lists and content that genuinely provides value, minimizing any characteristics that might flag your email as unsolicited bulk, even if permitted.
• Review Microsoft Documentation: Regularly consult official Microsoft documentation for the most up-to-date information on BCL values and their impact, as these systems evolve.
• Correlation with Complaints: While BCL itself doesn't directly cause complaints on consumer platforms, a higher BCL indicates that your email is more likely to be filtered to junk, which in turn can lead to users marking it as spam, thus generating the complaints you observe. This ties into how you get spam complaints.