What could cause email issues with high volume clients and no setting changes?

Key findings

• Unseen changes: Deliverability issues can arise even when no explicit settings have been altered, suggesting implicit changes in sending patterns or recipient engagement.
• ISP policy updates: Major email providers like Google, Yahoo, and Microsoft frequently update their bulk sender requirements. These changes can impact deliverability for high-volume senders even without changes on the sender's side. For instance, new rules were announced for bulk email senders from Google and Yahoo recently.
• Client behavior: Sometimes, clients inadvertently stop sending to specific large inbox providers like Gmail, leading to a sudden drop in volume for that particular domain. This can negatively affect sender reputation due to inconsistent sending patterns.
• Engagement shifts: A decline in recipient engagement (opens, clicks) or an increase in complaints can trigger deliverability filters, even if sending practices remain consistent.
• Hidden infrastructure problems: Issues such as IP address blocklisting, DNS misconfigurations, or SPF/DKIM authentication failures (perhaps due to third-party changes) might occur silently and impact deliverability.

Key considerations

• Monitor sending patterns: Even without setting changes, ensure consistent daily volume and frequency to major ISPs. Inconsistent sending can quickly lead to deliverability problems.
• Check ISP announcements: Stay informed about new bulk sender requirements from providers like Google, Yahoo, and Microsoft, as these can impact your sending practices. Our blog on email deliverability issues provides further insight.
• Review email authentication: Verify that your SPF, DKIM, and DMARC records are correctly configured and haven't been inadvertently altered or impacted by DNS changes.
• Analyze engagement metrics: Look for declines in open rates, click-through rates, or increases in spam complaints, which are strong indicators of a shifting sender reputation.
• Check blocklists: Even with consistent sending, an IP or domain could inadvertently land on a blocklist (or blacklist) due to factors beyond direct control. Consult an in-depth guide to email blocklists to learn more.

Key opinions

• Mistakes happen: Sometimes, the issue isn't a complex technical problem but a simple, accidental misconfiguration or stoppage of email flow to a specific provider, which can be hard to spot without proper monitoring.
• Low volume perception: For clients transitioning from very low to high volumes, deliverability issues can arise if the sending infrastructure isn't adequately warmed up or if the new volume triggers stricter ISP filters.
• ISP sensitivity: High-volume senders, even with good reputations, can experience throttling or filtering if they suddenly deviate from established patterns, even unintentionally, especially with major providers like Gmail and Microsoft.
• Engagement decay: Over time, even a consistent email program can see natural declines in engagement, leading to poorer inbox placement. Marketers need to actively manage list hygiene and content relevance.
• Platform nuances: The email service provider (ESP) or platform used might have internal changes or routing adjustments that affect deliverability without the marketer's direct knowledge.

Key considerations

• Proactive monitoring: Implement robust monitoring for deliverability, bounce rates, and spam placement across all major ISPs to quickly detect issues. Tools like Google Postmaster Tools can be invaluable.
• Segment by ISP: Analyze deliverability metrics for each major email provider (Gmail, Outlook, Yahoo, etc.) separately, as issues can be localized, as seen in the case of delivery problems to Gmail.
• Regular audits: Periodically audit sending practices and configurations, even if no issues are apparent. This includes checking list hygiene, content quality, and send frequency.
• Engagement measurement: Actively track user engagement to identify potential reputation declines before they lead to major deliverability blocks. A significant drop in open rates can be an early warning.
• Permission-based lists: Always ensure you have explicit permission to email subscribers. Not having permission is a primary reason emails go to spam.

Key opinions

• Reputation volatility: Sender reputation can degrade over time due to subtle shifts in recipient engagement or an increase in spam complaints, even if sending volume remains consistent. This can cause a sudden drop in domain reputation.
• Invisible blocklisting: An IP or domain might be privately blocklisted (or blacklisted) by an ISP without public notification, causing issues for specific destinations. This explains why emails might not be received with no bounce errors.
• Content filtering changes: ISPs continuously update their spam filters, meaning previously inboxed content might suddenly be flagged if new keywords, patterns, or image ratios are identified as problematic.
• Infrastructure quirks: Hidden DNS issues, subtle changes in mail server configurations (e.g., mail server updates), or network routing problems can manifest as deliverability errors without explicit sender-side changes.
• Authentication strictness: ISPs are becoming stricter with email authentication. While SPF, DKIM, and DMARC might be set up, a minor misalignment or a previously overlooked edge case can suddenly cause failures.

Key considerations

• Deep dive into logs: Examine mail server logs and DMARC reports for clues about rejection reasons or authentication failures, even for messages that don't bounce back explicitly. This can reveal issues like DKIM temperror.
• Segment by domain and IP: Isolating the issue to specific recipient domains or sending IPs can narrow down the cause, indicating targeted filtering or blacklisting. Understanding what happens when your IP gets blocklisted is essential.
• Warm-up for high volume: Even established high-volume senders can face issues if there are significant, unannounced shifts in their sending volume or patterns that require re-warming of IPs.
• External reputation checks: Regularly check public and private blocklists and use online tools to assess domain and IP reputation from an external perspective.
• Content audit: Review recent email content for new phrases, links, or attachments that might trigger spam filters, especially if content has become more promotional or less relevant over time.

Key findings

• Evolving compliance: New rules for bulk email senders from Google, Yahoo, and Microsoft (like Microsoft's HVE solution) indicate that standards are continuously evolving, requiring senders to adapt even without internal changes.
• Authentication enforcement: Documentation increasingly emphasizes strict SPF, DKIM, and DMARC alignment. Failures in these areas, even if previously tolerated, can now lead to outright rejections. Our guide on fixing DMARC issues can assist.
• Engagement signals: ISP documentation clearly states that positive engagement (opens, clicks) and low complaint rates are crucial for maintaining sender reputation and inbox placement.
• Spam complaints: Official guidelines emphasize that high spam complaint rates (even for legitimate mail) will lead to filtering. Changes in recipient reporting behavior can escalate this, even if content is unchanged.
• List hygiene: Documentation consistently recommends active list management to minimize bounces and reduce the risk of hitting spam traps.

Key considerations

• Review bulk sender guidelines: Regularly consult the official bulk sender guidelines for major ISPs, as these are frequently updated and dictate deliverability for high volumes. MarTech.org provides an excellent overview of new rules for bulk email senders.
• Adhere to technical standards: Ensure full compliance with RFCs and technical specifications for email sending. Even minor non-compliance can be penalized more severely by new ISP policies. Our article on RFC 5322 delves into this.
• Monitor complaint feedback loops: Sign up for and actively monitor FBLs (Feedback Loops) from ISPs to catch increases in spam complaints promptly. This is a critical indicator from the ISP's perspective.
• Manage sender reputation: Understand that ISPs dynamically assess sender reputation based on ongoing metrics, not just static configurations. Maintain good sending practices to ensure positive reputation.
• Throttling awareness: Be aware that high-volume sending to certain providers (like Exchange Online) can result in throttling if volume thresholds or policy requirements are exceeded, regardless of explicit 'setting changes'.