Why are email blocks and bounces higher than normal and are bot unsubscribes happening?

Key findings

• Widespread impact: Many senders are observing higher block and bounce rates across various mailbox providers (ISPs), not just specific ones. This suggests a broader trend or adjustment in filtering.
• ISP tightening: Mailbox providers like Gmail and Yahoo are perceived to be tightening their filtering criteria. This could be influenced by global cybersecurity concerns, leading to more aggressive spam detection.
• Bot unsubscribes: There are reports of email scanners or bots triggering one-click unsubscribes, making it difficult to differentiate legitimate user actions from automated ones. This phenomenon has an impact on email deliverability and reputation.
• Complaint bombing: Some senders are seeing long-term engaged subscribers suddenly complain on multiple past messages simultaneously, suggesting a potential bot-driven attack or malicious activity.

Key considerations

• Detailed analysis: Examine bounce reports for specific error codes and classify them as hard or soft bounces. Identify which mailbox providers are most affected to pinpoint potential issues, such as sudden spike in bounce rates from Gmail.
• Sender behavior: Before attributing issues to external factors, review your own sending practices, list hygiene, and content relevance. Often, problems can be traced back to internal processes.
• Bot detection: Implement robust bot detection mechanisms within your email platform and cross-reference ESP data with your internal user activity logs to identify suspicious unsubscribe or click behavior.
• Reputation monitoring: Regularly monitor your sender score and domain reputation to catch early warning signs of deliverability issues. High bounce rates negatively impact your Sender Score, leading to blocks.

Key opinions

• ISP tightening: Many marketers suspect that ISPs like Yahoo and Gmail are implementing stricter filtering mechanisms, which is contributing to the observed increase in blocks and bounces.
• Bot activity: A significant concern is the occurrence of bot-triggered one-click unsubscribes, which inflate unsubscribe numbers and affect list health metrics.
• Spam complaints: There are anecdotal reports of suspicious complaint patterns, where previously engaged subscribers submit multiple complaints at once, possibly indicating malicious bot activity.
• List hygiene impact: High bounce rates are a clear indicator of poor list hygiene and can lead to penalties like throttling, which directly impacts email campaigns.

Key considerations

• Verify unsubscribes: Marketers need to verify if unsubscribes are genuine user actions or bot-driven by cross-referencing ESP data with internal user engagement records. For more on this, see unusual clicks and unsubscribes.
• Data-driven decisions: Rely on deliverability data, even without official ISP confirmations, to identify trends and adapt sending strategies. Look for patterns in email bounce causes and fixes.
• Address reporting: Be prepared to explain changes in list size and engagement metrics to sales or other internal teams, backed by data on bot activity or deliverability challenges.
• Bounce management: Focus on minimizing bounce rates to boost ROI and maintain sender reputation, as high bounce rates can signal inactive or problematic email lists.

Key opinions

• Sender-specific issues: Most deliverability concerns for individual clients can be attributed to their own sending behaviors and practices rather than widespread external issues.
• Diagnostic approach: It is crucial to differentiate between soft and hard bounces and identify if issues are confined to specific mailbox providers or are occurring across the board.
• Reputation is key: A sudden drop in delivery often signals underlying issues with list quality or sending practices, which negatively affect IP and domain reputation, leading to increased blocks.
• Engagement signals: Mailbox providers increasingly rely on engagement metrics. Low engagement, especially with high sending volumes, can trigger higher scrutiny and filtering.

Key considerations

• Holistic review: Conduct a thorough review of your email program, including sending infrastructure, content, and list acquisition methods, as advised by expert deliverability checklists.
• Authentication: Ensure proper email authentication protocols (SPF, DKIM, DMARC) are configured and maintained to build trust with mailbox providers and prevent spoofing. Learn more about DMARC, SPF, and DKIM.
• Engagement metrics: Monitor engagement closely. Low engagement coupled with high volume can trigger increased scrutiny from ISPs, leading to blocks. Review bounce rates to identify inactive list segments.
• List hygiene: Regularly clean email lists to remove invalid or inactive addresses and known spam traps, as this is a fundamental step in preventing bounces and blocks.

Key findings

• Bounce definitions: A hard bounce signifies a permanent delivery failure (e.g., invalid address), while a soft bounce indicates a temporary issue (e.g., full mailbox).
• Primary causes: Common reasons for bounces include invalid or non-existent email addresses, recipient servers no longer existing, and strict security filters implemented by the recipient's ISP.
• Reputation impact: High bounce rates are a red flag for poor list hygiene and can lead to negative consequences for sender reputation, including throttling or being placed on blocklists.
• Spam trigger: Emails with elements perceived as spammy in the subject, body, or From address can trigger bounces or blocks from recipient servers, even if the address is valid.

Key considerations

• List validation: Regularly validate email lists to remove invalid addresses and reduce hard bounce rates, which are critical for maintaining good sender reputation. This prevents issues like sudden increases in Gmail hard bounces.
• Content review: Review email content, subject lines, and sender information to ensure they do not appear spammy to receiving servers. This directly impacts deliverability.
• SMTP error codes: Understand the meaning of different SMTP bounce codes to accurately diagnose the root cause of delivery failures and implement appropriate solutions.
• Domain reputation: Be aware that an IP with a poor sender score due to high bounce rates can lead to Email Service Providers blocking your emails. For more information, see email marketing red flags.