Why are AOL and Yahoo emails bouncing and how can it be fixed?

Key findings

• Bounce types: Bounces can be soft, often including the TSS04 code, or hard, like email does not exist, particularly for Yahoo and Gmail addresses.
• Infrastructure shift: AOL's email addresses now leveraging Yahoo's infrastructure can cause senders to hit new, stricter volume thresholds they previously avoided.
• Unforeseen spikes: Bounce rate spikes can occur suddenly, even if sending practices have remained consistent. This often indicates a change in how the receiving ISP views your mail, perhaps due to increased complaints or a perceived shift to spam.
• New sign-up issues: A significant portion of bounces affecting new sign-ups with email does not exist errors may point to issues with real-time validation or list acquisition processes.

Key considerations

• Email authentication: Ensure your domain has correctly configured SPF, DKIM, and DMARC records. These records are crucial for validating your sending domain and preventing email authentication failures, a common reason for bounces.
• List hygiene: Regularly clean your email list by removing unengaged or inactive contacts. This practice minimizes bounces and improves overall sender reputation. Consider also why soft bounces might be occurring for a proactive approach.
• Throttling sends: For specific domains like AOL and Yahoo, consider throttling your email volume over longer periods (hours or days) to avoid hitting arbitrary rate limits. The eM Client forum highlights that most global mail servers now require specific records in all sending domains.
• Monitoring and analysis: Pay close attention to bounce codes and patterns. Identifying the specific type of bounce (e.g., TSS04) can provide clues to the underlying problem, whether it's related to content, volume, or reputation. Add required records to your domain.

Key opinions

• Spike in bounces: Many marketers report experiencing sudden spikes in AOL bounces, sometimes appearing out of nowhere.
• TSS04 soft bounces: The TSS04 bounce text from Yahoo indicates potential issues with complaints or a spam pattern.
• Infrastructure merger impact: The shift of AOL addresses to Yahoo's infrastructure is believed to cause senders to cross previously unreached thresholds, leading to more bounces.
• New subscriber issues: A high percentage of bounces are observed for newly signed-up users, with errors like email does not exist, even for seemingly valid addresses. For more on this, see why valid addresses bounce.

Key considerations

• List hygiene importance: Regularly cleaning email lists, especially removing less engaged contacts, can significantly reduce bounce rates.
• Engagement strategy: Prioritizing sending to highly engaged users and adjusting automated flows based on initial engagement (e.g., opens) can help mitigate bounces. This also helps when AOL and Yahoo flag emails as spam.
• Send throttling: Throttling delivery over longer periods, sometimes hours or days, can alleviate pressure on Yahoo and AOL servers. HubSpot community indicates this type of error tends to occur when throttling happens.
• Complaint impact: A sudden increase in complaints can trigger soft bounce activity and signal to ISPs that your sending patterns resemble spam.

Key opinions

• Complaint correlation: The TSS04 error for Yahoo soft bounces often correlates with increased user complaints or indicates a pattern that is being flagged as spam.
• Threshold impacts: Experts suggest that the integration of AOL addresses into Yahoo's (Verizon Media's) infrastructure means senders might exceed volume thresholds they previously did not, leading to increased bounce rates. Understanding high bounce rates from Verizon is key.
• List hygiene efficacy: Consistent list hygiene, including the removal of inactive or less engaged contacts, is a fundamental strategy to prevent bounces and improve deliverability. This also reduces the chances of your emails being blocked by Yahoo/AOL.
• Volume management: Paring down sending volume and prioritizing engaged users, alongside throttling delivery, are proven methods to improve inbox placement and reduce bounces.

Key considerations

• Reputation monitoring: Even without changes in sending behavior, sudden increases in bounces may indicate a shift in your domain or IP reputation, necessitating diligent reputation monitoring.
• Bounce differentiation: Understanding the distinction between hard and soft bounces is critical for proper diagnosis and corrective action. For example, broken bounce handling can lead to further issues.
• Engagement segmentation: Segmenting your audience by engagement levels and sending fewer emails to less active users can significantly improve deliverability to sensitive providers like AOL and Yahoo.
• Blocklist implications: Increased bounces can lead to your domain or IP being placed on an email blocklist (or blacklist), which will further impair your deliverability. Learn what being blacklisted means.

Key findings

• Authentication requirements: Mail servers, including those used by Yahoo and AOL, increasingly require proper authentication records (SPF, DKIM, DMARC) for all sending domains to accept incoming mail. Learn how to fix DMARC failing for Yahoo/AOL.
• Spam blocking: Repeated delivery failure errors to AOL Mail customers are frequently attributed to spam blocking on AOL's servers, emphasizing the need for good sending practices.
• Throttling and soft bounces: Soft bounces can occur when ISPs like Yahoo/AOL decide to throttle emails due to various factors, including volume or perceived suspicious patterns. For more information, read about soft bounce errors.
• Account management: Yahoo has historically purged abandoned or inactive accounts, which can lead to legitimate-looking addresses suddenly bouncing as non-existent.

Key considerations

• Compliance with policies: Adhering to the specific policies and guidelines published by AOL, Yahoo, and their parent company (Oath/Verizon Media) is crucial for consistent deliverability. This includes understanding the troubleshooting DMARC reports from these providers.
• Filter and block settings: For recipients, AOL's help documentation advises checking personal email filters and block settings as a first step if emails are not being received. Fix problems receiving AOL Mail.
• Content and attachments: Problems with viewing images or attachments in emails can sometimes be related to how the email is formatted or perceived by the receiving server, potentially contributing to non-delivery or spam flagging.
• Security breaches impact: Past security breaches at Yahoo and AOL have influenced their stronger spam defenses and DMARC enforcement, which can impact mailing lists and forwarding.