Summary
Yahoo blocks emails with a TSS04 error due to a combination of factors including spam-like sending patterns, poor sender reputation, DNS configuration issues, lack of email authentication, and poor list hygiene. If Yahoo considers your mail spam, they will block you. Core issues include not acquiring and filtering lists of users in the right way, using a dodgy IP address, or poorly written content
Key findings
- Spam-Like Sending Patterns: Yahoo identifies and blocks sending behavior resembling spam based on patterns and recipient complaints.
- Poor Sender Reputation: Spam complaints, blacklistings, low engagement, and hitting spam traps damage sender reputation, leading to TSS04 errors.
- DNS Configuration Issues: DNS resolution failures prevent Yahoo from verifying the sender's domain, resulting in blocks.
- Lack of Email Authentication: Incorrect or missing SPF, DKIM, and DMARC records hinder Yahoo's ability to authenticate the sender.
- Poor List Hygiene: Sending emails to invalid or inactive addresses and using unknown or unverified lists negatively impacts sender reputation.
Key considerations
- Review Sending Practices: Eliminate spam-like practices, prioritize recipient consent, and ensure emails are sent to engaged users.
- Monitor and Improve Sender Reputation: Actively monitor sender reputation using tools like Google Postmaster Tools, address spam complaints, and improve engagement rates.
- Verify DNS Configuration: Ensure proper DNS configuration, including MX records and reverse DNS, to enable Yahoo to verify the sender's domain.
- Implement Email Authentication: Correctly configure SPF, DKIM, and DMARC records to authenticate email sending domains and enhance deliverability.
- Practice List Hygiene: Regularly clean email lists to remove invalid or inactive addresses, implement opt-in processes, and segment lists for targeted content.
- Follow IP Warm-up Best Practices: Gradually increase sending volume when using new IPs or domains to build a positive reputation with Yahoo.
What email marketers say
10 marketer opinions
Yahoo blocks emails with a TSS04 error due to various factors related to sender reputation, authentication, content, and infrastructure. Using unknown lists is risky, and incorrect email authentication records can lead to blocks. Sudden increases in email volume, spam-like content, and improper DNS configuration are also culprits. Newly assigned or previously used for spam IPs, using shared IPs for high-volume sending, failing to segment lists, and employing spam trigger words can trigger TSS04 errors. Gradual IP warm-up is also crucial.
Key opinions
- List Quality: Using unknown or unverified email lists significantly increases the risk of being blocked by Yahoo.
- Authentication: Incorrect or missing email authentication records (SPF, DKIM, DMARC) are a primary cause of TSS04 errors.
- Sending Volume: Sudden increases in email volume, especially from new IPs, trigger Yahoo's spam filters.
- Content: Spam-like content, deceptive subject lines, and spam trigger words can lead to blocks.
- Infrastructure: Improper DNS configuration and using IPs with a poor reputation contribute to TSS04 errors.
Key considerations
- List Hygiene: Implement rigorous list cleaning and opt-in processes to ensure recipients are genuinely interested in receiving emails.
- Authentication Setup: Correctly configure SPF, DKIM, and DMARC records to authenticate email sending domains.
- IP Warm-up: Gradually increase email volume when using new IPs or domains to establish a positive sending reputation.
- Content Review: Carefully review email content, subject lines, and links to avoid spam triggers and maintain relevance for recipients.
- Infrastructure Check: Ensure proper DNS configuration and monitor IP reputation to prevent delivery issues.
- List Segmentation: Divide email lists into smaller segments based on demographics, behavior, or other relevant criteria to ensure that each recipient receives only the most relevant content.
Marketer view
Email marketer from EmailGeeks mentions that the content of the email, including links, images, and text, can trigger spam filters. If the content is similar to spam or contains suspicious elements, Yahoo may block the email with a TSS04 error.
21 Jan 2025 - EmailGeeks
Marketer view
Email marketer from Reddit explains that a common cause for TSS04 errors is improper DNS configuration, particularly with the domain's MX records or reverse DNS records. This prevents Yahoo from verifying the sender's server.
5 Jan 2023 - Reddit
What the experts say
7 expert opinions
Yahoo's TSS04 error often indicates that Yahoo perceives the sender's practices as spam-like, driven by patterns of sending unwanted mail. Diagnosing the issue requires analyzing bounce messages, identifying rejection reasons (DNS, reputation, content), and actively managing sender reputation through proper list hygiene. Delivering mail people want, and getting their consent, are the fundamentals of email delivery.
Key opinions
- Spam-Like Practices: Yahoo identifies sending patterns that resemble spam, leading to blocks regardless of technical configurations.
- Sender Reputation: Sender reputation is a major determinant of deliverability; factors like spam complaints and low engagement significantly impact it.
- List Hygiene: Poor list hygiene, resulting in sending to invalid or inactive addresses, negatively affects sender reputation and delivery.
- Consent and Relevance: Sending mail that recipients don't ask for and don't want results in blocks.
- Troubleshooting: Diagnosing TSS04 requires checking bounce messages and identifying the root cause of the rejection (e.g., DNS, content).
Key considerations
- Eliminate Spam-Like Behavior: Review and adjust sending practices to avoid triggering spam filters and prioritize recipient consent.
- Monitor and Manage Reputation: Actively monitor sender reputation through feedback loops, address spam complaints, and ensure high engagement rates.
- Implement List Cleaning: Regularly clean email lists to remove inactive or invalid addresses to maintain a healthy sending reputation.
- Obtain Explicit Consent: Ensure that recipients have explicitly opted in to receive emails and are genuinely interested in the content.
- Analyze Bounce Messages: Thoroughly analyze bounce messages to identify specific reasons for delivery failures and implement appropriate fixes.
Expert view
Expert from Email Geeks states that the described sending behavior sounds like normal spammer behavior, and if recognized as such by Yahoo, there might not be much that can be done to get mail delivered on an ongoing basis.
16 Apr 2023 - Email Geeks
Expert view
Expert from Spam Resource emphasizes that sender reputation is critical for Yahoo delivery. Factors like spam complaints, blacklistings, and low engagement rates can negatively impact reputation and lead to TSS04 errors. Actively monitoring and managing reputation is essential.
14 May 2025 - Spam Resource
What the documentation says
5 technical articles
Documentation indicates that Yahoo's TSS04 error is primarily triggered by issues related to DNS configuration and poor sender reputation. DNS resolution failures prevent Yahoo from verifying the sender's domain. A low sender reputation, influenced by spam complaints, blacklistings, low engagement, and hitting spam traps, leads to Yahoo blocking the emails.
Key findings
- DNS Configuration: DNS resolution errors are a direct cause of TSS04, preventing Yahoo from verifying the sender's domain.
- Sender Reputation: A poor sender reputation, resulting from spam complaints, blacklistings, and low engagement, leads to TSS04 errors.
- Spam Traps: Sending emails to spam traps severely damages sender reputation and contributes to TSS04 blocks.
Key considerations
- Verify DNS Settings: Ensure proper DNS configuration, including MX records and reverse DNS, to allow Yahoo to verify the sender's domain.
- Monitor Reputation: Actively monitor sender reputation using tools like Google Postmaster Tools and address issues like spam complaints and blacklistings promptly.
- Practice List Hygiene: Maintain clean lists by removing invalid or inactive addresses and implementing opt-in processes to avoid sending emails to spam traps and improve engagement.
Technical article
Documentation from Google Postmaster Tools explains that low engagement metrics and high spam complaints can negatively impact sender reputation with various ISPs, including Yahoo, leading to blocks and errors like TSS04.
18 Jan 2025 - Google
Technical article
Documentation from SparkPost explains that sending emails to spam traps can severely damage sender reputation and result in blocks like TSS04 errors. Maintaining clean lists and practicing proper list hygiene is essential.
15 Oct 2023 - SparkPost Documentation
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