Resolving Yahoo soft bounces and TSS04 errors when warming up email sending too quickly involves several key steps. Primarily, slowing down the warm-up process is crucial, reducing sending to previously successful levels and gradually increasing volume. Focusing on engaged recipients and maintaining a clean email list are also important. Additionally, understanding and addressing the underlying causes of bounces, such as permission issues or spam triggers, and complying with Yahoo's sending guidelines, including DMARC requirements, are essential. Monitoring deliverability metrics and understanding bounce codes can provide insights. Opening a postmaster ticket with Yahoo might be necessary in some cases.
11 marketer opinions
To resolve Yahoo soft bounces and TSS04 errors caused by rapid email warm-up, a multi-faceted approach is necessary. Experts recommend a slow and steady warm-up process, beginning with a small volume of emails sent to highly engaged users and gradually increasing the volume over time. Maintaining a clean email list by removing inactive or bounced subscribers is also important. Additionally, it's crucial to focus on engagement metrics, segment email lists for targeted content, properly authenticate emails with SPF, DKIM, and DMARC, and monitor deliverability metrics regularly. Reading Yahoo error codes can provide information about the issues, submitting feedback forms to Yahoo can help resolve the issue, and making sure that email content is high-quality and personalized will also help.
Marketer view
Email marketer from Email Geeks shares their experience of encountering TSS04/IPTS04 errors across multiple ESPs simultaneously despite consistent sending patterns. They explain that submitting feedback forms to Yahoo resolved the issues, and advise to reply to generic responses requesting further investigation with data and explanations.
25 Nov 2021 - Email Geeks
Marketer view
Email marketer from EmailDrip shares that a slow and steady approach to warming up your IP address is essential, starting with a small number of emails to highly engaged users and gradually increasing the volume. This helps establish a positive reputation with ISPs like Yahoo.
24 Jun 2022 - EmailDrip
6 expert opinions
Resolving Yahoo soft bounces and TSS04 errors, especially when warming up too fast, requires a comprehensive approach. Experts advise slowing down the warm-up process to previously successful sending levels and focusing on engaged recipients. Understanding Yahoo's spam escalation process, from spam folders to rate limiting, is crucial. Avoid aggressively removing soft bounces as they signal underlying issues. Investigating potentially problematic links, opening a postmaster ticket with Yahoo, and building a positive sender reputation are important steps. Furthermore, compliance with Yahoo and AOL's enhanced DMARC enforcement is necessary to prevent authentication failures and improve deliverability.
Expert view
Expert from Email Geeks shares that Yahoo escalates spam handling through stages: spam folder for unengaged and new recipients, then existing recipients, then all mail, followed by rate limiting, stronger rate limiting, and finally blocking. They suggest looking back 6 months to review engagement and open rates, especially considering Yahoo's pixel pre-fetching.
2 Nov 2023 - Email Geeks
Expert view
Expert from Email Geeks advises against aggressively removing soft bouncing addresses due to Yahoo using soft bounces as a signal. They recommend fixing the underlying issues causing recipient complaints before removing them. They also suggest investigating links in the message that might have a bad reputation.
5 Nov 2021 - Email Geeks
4 technical articles
Resolving Yahoo soft bounces and TSS04 errors, particularly during email warm-up, involves understanding and addressing the underlying causes. Official documentation emphasizes reviewing sending practices, focusing on permission, list hygiene, and content relevance. While TSS04 is specific to Yahoo, a broader understanding of bounce codes and general email sending best practices, such as using authentication methods (SPF, DKIM, DMARC), maintaining a clean list, avoiding spam triggers, and monitoring sending reputation and bounce rates, are universally applicable to preventing deliverability issues.
Technical article
Documentation from SparkPost explains that understanding bounce codes is crucial for troubleshooting delivery issues. While TSS04 is specific to Yahoo, other soft bounce codes can provide insights into potential problems with your sending reputation and practices.
26 Nov 2023 - SparkPost
Technical article
Documentation from Microsoft shares while focusing on Microsoft services, the document emphasizes the importance of following best practices for bulk email sending to maintain a good reputation. This includes proper list management, avoiding spam triggers in content, and monitoring bounce rates to quickly address issues affecting deliverability.
3 Jun 2021 - Microsoft
Do Yahoo and Gmail require DMARC authentication for senders?
How can I troubleshoot and resolve Yahoo TSS04 email errors?
How do I warm up a new IP address for transactional emails?
How do I contact the Yahoo postmaster for deliverability issues during IP warm-up?
How can I resolve Yahoo SMTP error 421 4.7.0 TSS04?
How do I contact Yahoo Sender Support?
© 2025 Suped Pty Ltd