Why are Yahoo messages being permanently deferred with TSS11 error?
Summary
What email marketers say9Marketer opinions
Email marketer from Stack Overflow shares that TSS11 usually means Yahoo has identified your email server IP as a source of spam, or your sending practices violate their policies. You need to contact Yahoo postmaster support to resolve this.
Email marketer from Mailjet states that a poor sender reputation can trigger TSS11 errors. Improving sender reputation involves consistent sending volume, low complaint rates, and proper email authentication.
Email marketer from Reddit explains that a likely cause is a sudden increase in email volume or a change in the content that triggered Yahoo's spam filters. Check your recent campaigns and sending practices.
Email marketer from Yahoo Postmaster Tools explains that a TSS11 error indicates that all messages from a particular IP address are being permanently deferred. Retrying will not succeed. This typically means Yahoo has strong concerns about the sending practices or the content originating from that IP address.
Email marketer from Litmus explains low engagement rates (opens, clicks) can negatively impact sender reputation, leading to deliverability problems like TSS11 errors. Try re-engaging inactive subscribers or removing them.
Marketer from Email Geeks suggests working with their postmaster team, as they have likely escalated the issue internally to review the traffic and determine if it's being treated correctly. They also suggest the IP address or its traffic may be problematic. They further suggest reviewing outbound traffic from the IP, and considering that past good performance doesn't guarantee current good behavior.
Email marketer from GMass responds that Yahoo may be deferring email with a TSS11 error because of too many emails sent in a short timeframe. Throttling can help.
Email marketer from Email Marketing Forum explains Yahoo and other ISPs monitor complaint rates closely. High complaint rates are a strong signal of spam and can result in blocked emails or TSS11 errors. Monitor and address complaints promptly.
Email marketer from Email on Acid recommends checking your IP address against common email blocklists. Being listed on a blocklist can lead to delivery issues, including TSS11 errors from Yahoo. Use tools to perform blocklist checks.
What the experts say3Expert opinions
Expert from Word to the Wise says that if Yahoo is blocking mail with a TSS11 error, it is critical to double-check list hygiene, ensure you are not sending to spam traps or unengaged users, and to have feedback loops and complaint processing in place. Often these types of errors point to sudden increases in sending to bad email addresses.
Expert from Email Geeks explains that something must have changed recently, such as a new list, different content, compromised domain, or compromised account. Suggests reviewing changes in the week or two before the bounces started.
Expert from Spam Resource explains that Yahoo's TSS11 error often points to a problem with your sending reputation, content filtering issues, or authentication failures (SPF/DKIM). The specific cause needs direct investigation with Yahoo's postmaster team.
What the documentation says4Technical articles
Documentation from SparkPost explains that a TSS11 error often means that Yahoo's systems have detected a pattern of behavior that they consider abusive, such as sending to a large number of invalid or spam-trapped email addresses. Review your list hygiene practices.
Documentation from RFC Editor explains that 5.7.2 Enhanced Mail System Status Code indicates delivery was refused because the message's content did not meet standards or because of other content or policy reasons.
Documentation from Microsoft explains that DMARC policies, including strict enforcement, can cause rejections if your emails fail authentication checks (SPF or DKIM). A TSS11 error might be linked to DMARC failures.
Documentation from Dmarcian explains you should check your SPF/DKIM. Yahoo and other ISPs rely on these authentication methods to verify that emails are legitimately sent from your domain. Incorrect or missing SPF/DKIM records can cause delivery problems.