Why am I seeing an influx of TS errors from Yahoo?

Key findings

• Error increase: Senders have reported a noticeable surge in TS errors from Yahoo domains, often appearing over several hours or days.
• Delivery persistence: Despite receiving error messages, many emails are still successfully delivered, and outbound mail queues are not experiencing significant delays.
• Throttling indicators: The errors often accompany MTA backoff notifications, indicating that Yahoo's servers are temporarily throttling incoming connections.
• Server transitions: Observations suggest Verizon Media Group (VMG) might be actively switching between different mail transfer agents, like MTA and ATLAS.
• Engaged senders affected: Even highly engaged email streams are seeing these errors, pointing to a broader system-level issue.

Key considerations

• Continuous monitoring: Keep a close eye on your email logs and deliverability rates to detect any shift from transient errors to persistent bouncebacks.
• Authentication check: Ensure your DMARC, SPF, and DKIM records are correctly configured to maintain sender trust.
• Reputation management: A strong sender reputation can help mitigate the impact of temporary ISP anomalies. For more information, read about issues with Yahoo mail bounce backs.
• Avoid overreaction: Unless actual delivery failures increase, drastic changes to sending practices might not be necessary.

Key opinions

• Shared experience: Many marketers quickly confirmed they were seeing the same increased TS errors from Yahoo, suggesting a widespread phenomenon.
• Errors without bounces: A key point of discussion was that despite the errors, hard bounces were not increasing, and mail was generally getting through.
• MTA backoffs noted: Some reported receiving MTA backoff notifications, indicating Yahoo's systems were intentionally slowing down inbound connections rather than rejecting them.
• Timing of errors: The issues often started in the late afternoon or evening and continued into the next day, consistent across different senders.
• Throttling confirmed: Marketers identified an increase in throttling for all Verizon Media Group domains.

Key considerations

• Log analysis: Thoroughly reviewing MTA logs is essential to understand the specific nature and frequency of these errors.
• Error differentiation: It's important to distinguish between temporary TS errors that allow retries and permanent rejections.
• Impact assessment: Assess the overall impact on your email deliverability rather than reacting solely to error messages. For more information, read about issues with Yahoo mail bounce backs.
• Internal communication: Keep relevant internal teams informed about the observed issues and any potential, albeit temporary, impacts.

Key opinions

• Infrastructure changes: Experts believe these errors frequently stem from Yahoo's (VMG) backend system adjustments or maintenance activities affecting their MTAs.
• Temporary throttling: The TS errors, particularly when coupled with MTA backoffs, are often a sign of temporary throttling mechanisms designed to manage server load.
• Server transitions: Direct observations of VMG switching between MTA and ATLAS servers strongly suggest ongoing, impactful infrastructure changes.
• Systemic vs. sender: Widespread, sudden error spikes are usually indicative of ISP-side systemic issues, rather than individual sender reputation problems.
• Error types: Experts emphasize differentiating between transient errors (which permit retries) and hard bounces (permanent failures), as the former is less critical.

Key considerations

• Measured response: Experts advise against making drastic changes to sending practices unless there's clear evidence of widespread delivery failures or queue congestion.
• List hygiene: Consistent list cleaning practices are always important to minimize negative impacts from any deliverability challenges.
• DMARC monitoring: Utilize DMARC aggregate reports to gain insights into authentication and overall delivery trends with ISPs like Yahoo.
• Authentication validity: Regularly check and troubleshoot DMARC issues to ensure authentication protocols are correctly configured and aligned.

Key findings

• Temporary conditions: Documentation confirms that TS (temporary service) errors signify a temporary issue, not a permanent rejection.
• Retry mechanism: Standard protocols mandate that sending mail transfer agents (MTAs) should retry messages after receiving a transient error.
• Throttling acknowledged: ISP documentation often details that temporary errors are a way to implement rate limiting or throttling to manage network abuse or load.
• Maintenance impact: Server maintenance or upgrades are common causes for temporary service disruptions and increased error messages.
• Authentication importance: Adherence to email authentication standards (SPF, DKIM, DMARC) is consistently emphasized for reliable email delivery.

Key considerations

• RFC compliance: Verify that your MTA is correctly configured to handle and retry transient SMTP errors as per internet standards.
• Postmaster guidelines: Regularly consult postmaster guidelines from major ISPs like Yahoo for specific error explanations and best practices.
• Rate limit adherence: Ensure your sending practices respect documented rate limits and connection policies to avoid triggering aggressive throttling or blocklisting. For more information, read our simple guide on how email blacklists work.
• DMARC record examples: Maintain valid and correctly configured DMARC records to pass authentication checks, which are crucial for consistent deliverability. Explore simple DMARC record examples.