Summary
In February 2022, email senders experienced increased blocking and deliverability issues with Yahoo and AOL. Observed issues include 421 and TSS04 errors, particularly affecting dedicated IPs, with system-wide deferrals starting around February 24th. The reasons are multifaceted, including potential filtering related to the war in Ukraine, and standard deliverability pitfalls. Key issues identified span from temporary server failures to problems with reputation, blacklisting and sender authentication. Addressing these issues involves ensuring permission-based sending, maintaining strict list hygiene, monitoring sender reputation, implementing proper email authentication (SPF, DKIM, DMARC) and ensuring keys are rotated properly, checking and responding to blocklists, warming up new IPs gradually, reducing spam complaints, and personalizing emails through segmentation. Following Yahoo's best practices for bulk sending is also crucial.
Key findings
- Yahoo/AOL Blocking: Emails were being blocked or deferred by Yahoo/AOL, indicated by 421 and TSS04 errors, especially affecting dedicated IPs.
- System-Wide Deferrals: Deferrals began around February 24th and were system-wide, without a clear specific cause.
- Authentication Issues: Lack of proper email authentication (SPF, DKIM, DMARC) is a significant contributing factor to deliverability problems.
- Reputation Impact: Poor sender reputation and being listed on blocklists lead to emails being blocked or sent to spam.
- Ukraine War Filter: A possible trigger was speculated to be related to Yahoo filter reacting to potential malicious traffic caused by the war in Ukraine.
- Temporary Server Issues: 421 errors indicate temporary server overload or connection limits, requiring retries.
- DMARC policy: Incorrect DMARC policies can result in AOL and Yahoo blocking emails.
- DKIM key rotation: DKIM Key rotation can cause issues if overlap between old and new keys does not occur.
- Lack of Permission: Sending emails without explicit permission, especially to AOL, leads to being marked as spam and blocked.
Key considerations
- Implement Best Practices: Adhere to bulk sending best practices outlined by Yahoo and AOL, focusing on authentication and list management.
- Implement DMARC: Implement and correctly configure DMARC to prevent spoofing and improve deliverability. Be sure to manage policy correctly and key rotations overlap
- Monitor Reputation: Monitor sender reputation and take steps to improve it, including IP warm-up for new IPs.
- Implement Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) is in place to verify sender legitimacy.
- Maintain List Hygiene: Regularly clean email lists by removing inactive subscribers and bounces to improve sender reputation.
- Monitor Blocklists: Check sending IPs and domains against blocklists and take steps to get removed if listed.
- Permission Based: Ensure the correct permission is gained before any email activity occurs.
- Retry Logic: Implement retry logic in sending infrastructure to handle temporary rejections due to greylisting or rate limits.
- Gradual Increase: Gradually increase sending volume when making changes and monitor impact
- Personalize: Personalize emails through segmentation to improve engagement and reduce spam complaints.
- Follow RFC: Check to ensure compliance with RFC and associated standards
What email marketers say
14 marketer opinions
In February 2022, email marketers observed increased blocking and deliverability issues specifically with Yahoo and AOL. These problems manifested as 421 errors, TSS04 errors, and system-wide deferrals, particularly affecting dedicated IPs. Contributing factors identified include potential filtering related to the war in Ukraine, and standard deliverability pitfalls. Addressing these issues involves verifying IP reputation, ensuring proper email authentication (SPF, DKIM, DMARC), warming up new IPs gradually, managing list hygiene, reducing spam complaints, personalizing emails through segmentation, and checking blocklist status. Some experts point towards temporary server issues and greylisting as potential causes for rejection.
Key opinions
- Yahoo/AOL Blocking: Emails were being blocked or deferred by Yahoo/AOL, evidenced by 421 and TSS04 errors, especially affecting dedicated IPs.
- System-Wide Deferrals: Deferrals began around February 24th and were system-wide, without a clear specific cause.
- Authentication Issues: Lack of proper email authentication (SPF, DKIM, DMARC) is a significant contributing factor to deliverability problems.
- Reputation Impact: Poor sender reputation and blocklisting lead to emails being blocked or sent to spam.
- Ukraine War Filter: A possible trigger was speculated to be related to Yahoo filter reacting to potential malicious traffic caused by the war in Ukraine.
Key considerations
- Check Reputation: Monitor sender reputation and take steps to improve it, including IP warm-up for new IPs.
- Implement Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) is in place to verify sender legitimacy.
- Maintain List Hygiene: Regularly clean email lists by removing inactive subscribers and bounces to improve sender reputation.
- Monitor Blocklists: Check sending IPs and domains against blocklists and take steps to get removed if listed.
- Gradual Increase: Gradually increase sending volume when making changes and monitor impact
- Personalize: Personalize emails through segmentation to improve engagement and reduce spam complaints.
- Retry Logic: Implement retry logic in sending infrastructure to handle temporary rejections due to greylisting or rate limits.
Marketer view
Marketer from Email Geeks saw the Yahoo/AOL inboxing issues, with the 25th being slightly better but then cropping back up.
18 Mar 2023 - Email Geeks
Marketer view
Email marketer from Validity Blog discusses the importance of maintaining a clean email list by removing inactive subscribers and bounces. They highlight that a high bounce rate can negatively impact sender reputation and deliverability.
31 Mar 2024 - Validity Blog
What the experts say
2 expert opinions
Experts suggest email blocking by Yahoo and AOL stems from poor sender reputation, spam complaints, lack of authentication (SPF, DKIM, DMARC), and blacklisting. Permission-based marketing and strict list hygiene are critical, especially with AOL, as sending unsolicited emails will likely result in being marked as spam and subsequently blocked.
Key opinions
- Poor Sender Reputation: A low sender reputation increases the likelihood of emails being blocked.
- Lack of Authentication: Failure to implement SPF, DKIM, and DMARC can lead to deliverability issues.
- Blacklisting: Being listed on blocklists results in emails being blocked by ISPs.
- Importance of Permission: Explicit permission is critical, especially with AOL, as unrequested emails are often flagged as spam.
Key considerations
- Monitor Reputation: Actively monitor your sender reputation and take corrective actions if it's low.
- Implement Authentication: Set up SPF, DKIM, and DMARC to authenticate emails and prove legitimacy.
- Manage Spam Complaints: Actively manage spam complaints to reduce the negative impact on your reputation.
- Maintain List Hygiene: Regularly clean your email list to remove inactive subscribers and ensure only permission-based contacts are included.
Expert view
Expert from Word to the Wise (Laura Atkins) discusses the importance of permission and list hygiene for email marketing, especially with AOL. She emphasizes that if you lack explicit permission to send emails, your messages will likely be treated as spam, leading to blocking. Regular cleaning of your email list is therefore a vital part of your email strategy.
21 Aug 2023 - Word to the Wise
Expert view
Expert from SpamResource explains that email blocking can occur due to factors like poor sender reputation, spam complaints, lack of authentication, or being listed on blocklists. They suggest monitoring sender reputation, authenticating emails using SPF, DKIM, and DMARC, and actively managing spam complaints to improve deliverability.
9 Jul 2021 - SpamResource
What the documentation says
5 technical articles
Documentation indicates that email blocking by Yahoo and AOL in February 2022 can be attributed to several factors. Temporary failures, indicated by 421 status codes, may result from server overloads or connection limits, suggesting retrying. Adhering to bulk sending best practices, including authenticating emails (SPF, DKIM, DMARC), responsibly managing email lists, and monitoring sender reputation, is crucial, as non-compliance leads to blocking. DMARC implementation safeguards against spoofing and phishing, enhancing deliverability. Furthermore, improper DKIM key rotation and DMARC policy issues could also cause email blocking by AOL and Yahoo.
Key findings
- 421 Status Codes: 421 status codes signify temporary server failures, like overload or connection limits, suggesting a retry.
- Bulk Sending Practices: Failure to adhere to Yahoo's bulk sending best practices, including authentication and responsible list management, leads to blocking.
- DMARC Implementation: Implementing DMARC protects against spoofing and phishing, improving deliverability.
- DKIM Key Rotation: DKIM Key rotation can have issues if not handled correctly.
- DMARC Policy Issues: Incorrect DMARC policies can result in AOL and Yahoo blocking emails.
Key considerations
- Implement Best Practices: Adhere to bulk sending best practices outlined by Yahoo, focusing on authentication and list management.
- Implement DMARC: Implement and correctly configure DMARC to prevent spoofing and improve deliverability.
- Retry Failed Sends: Implement a retry mechanism for sends that initially receive a 421 status code.
- DKIM Key Rotation: Ensure that when rotating DKIM keys overlap between old and new keys occurs.
- DMARC Policy: Carefully review and configure DMARC policies to avoid unintended blocking by AOL and Yahoo.
Technical article
Documentation from DMARC.org explains that implementing DMARC helps protect your domain from email spoofing and phishing attacks, which can improve deliverability. They detail the steps involved in creating and publishing a DMARC record and monitoring its impact.
16 Nov 2022 - DMARC.org
Technical article
Documentation from SocketLabs.com explains that AOL and Yahoo Mail blocking emails due to DMARC policy issues.
26 Oct 2021 - SocketLabs.com
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