How to resolve Verizon Media email blocking and TSS04 errors?
Matthew Whittaker
Co-founder & CTO, Suped
Published 29 Jul 2025
Updated 19 Aug 2025
7 min read
Encountering email blocking from Verizon Media Group, which includes Yahoo and AOL, can be incredibly frustrating. One of the most common error codes you might encounter is TSS04. This code signals that your messages are being temporarily deferred, often due to user complaints or perceived unwantedness. When you're dealing with these issues, it can feel like your emails are stuck in an infinite loop, especially if you've already tried basic troubleshooting.
I've seen many senders struggle with this particular blocklist, as it often means that even emails from engaged subscribers aren't reaching the inbox, or they are landing directly in the spam folder. This can severely impact your communication efforts, whether for marketing, transactional, or operational emails. The key to resolving these issues is understanding the underlying causes and implementing a comprehensive strategy.
This guide will walk you through diagnosing and resolving Verizon Media email blocking and TSS04 errors, providing actionable steps to improve your email deliverability and ensure your messages reach their intended recipients.
Understanding Verizon Media’s blocking mechanisms
When you see a TSS04 error from Verizon Media, it almost always points to a problem with user complaints or the perceived unwantedness of your mail. This isn't just a generic block, it's a specific signal that recipients are actively marking your emails as spam, or your engagement metrics (like opens and clicks) are too low, indicating that your mail isn't wanted.
Verizon Media's systems are designed to protect their users' inboxes from unwanted mail. They use a sophisticated set of algorithms to determine a sender's reputation, and high complaint rates are a major red flag. Even a small number of complaints can trigger a TSS04 block, especially if your sending volume is low. It's an important warning that precedes a more severe, persistent block.
One common scenario I've observed is when multiple entities or subsidiaries share the same dedicated IP address for sending. If even one of these entities has poor list acquisition practices or sends content that generates complaints, it can negatively impact the reputation of the entire IP, leading to TSS04 errors for all senders on that IP. This shared reputation aspect makes it challenging to pinpoint the exact source of the problem, requiring thorough detective work.
Understanding the problem
TSS04 errors: Indicate that your emails are being temporarily rejected due to perceived unwantedness or user complaints. This is an initial warning.
Spam folder delivery: Before a hard block, your emails might have been consistently landing in the spam folder, reducing engagement and increasing the likelihood of complaints.
Diagnosing the root cause
The first step in resolving TSS04 errors is to accurately diagnose the problem. It's crucial to look beyond the surface and identify the underlying causes, as postmaster responses (even from Verizon Media's own channels) can often be vague or unhelpful.
You should examine your bounce logs for the specific error message 421 4.7.0 [TSS04]. This confirms you are dealing with a Verizon Media related block. Keep in mind that a 421 or 451 SMTP error typically indicates a temporary problem, which means delivery might be delayed but not permanently blocked, although TSS04 is a serious warning that can lead to harder blocks if not addressed. You can find more information about these temporary errors on resources like Broadcom's support site.
Example TSS04 Bounce Message
421 4.7.0 [TSS04] Messages from [your.ip.address] temporarily deferred due to user complaints - 4.16.55.1; see https://postmaster.verizonmedia.com/error-codes
Even if your emails are currently going to the spam folder and you haven't seen recent complaints, the TSS04 error signifies a history of complaints. This means the underlying issue is that your recipients, at some point, did not want your mail. It's an escalation stage, implying that your mail has been directed to the bulk folder for a while. Therefore, it's crucial to review your mailstreams, list acquisition practices, and content to identify any problematic areas. This might include checking for your IP or domain on public email blocklists or blacklists, although TSS04 is typically not a blocklist issue, but rather a reputation issue directly with Verizon Media.
Strategic steps to resolve blocking
Resolving TSS04 errors requires a strategic approach focused on improving your sender reputation and aligning with Verizon Media's expectations for desired mail. The core issue is that your recipients don't want your mail, so the solution lies in improving permission and wantedness.
First, you need to step back and temporarily reduce your sending volume to Verizon Media domains (Yahoo, AOL, Verizon.net). This allows your sender reputation to recover from a low or bad state. Once you've paused, initiate campaigns with your most engaged subscribers who genuinely want your emails. This helps re-establish a positive sending history with Verizon Media. If your emails are still going to spam, check out our guide on why emails go to spam.
Focus on improving your list quality and content relevance. This includes implementing a strict double opt-in process, regularly cleaning your lists of inactive subscribers, and segmenting your audience to ensure you're sending the right content to the right people. For high-volume senders, creating separate lists for Verizon Media domains might be a good way to mitigate impact, as suggested in some deliverability best practices. Remember, improving permission and wantedness is the ultimate fix for these delivery problems.
Issue Area
Action to Take
Sender reputation
Temporarily halt or drastically reduce sends to Verizon Media domains. Begin sending to your most engaged subscribers to rebuild trust.
List quality
Implement strict opt-in processes. Remove inactive subscribers and re-engage dormant ones with targeted campaigns. Consider a re-permission campaign.
Content relevance
Ensure your content is valuable and relevant to your audience. Avoid spammy keywords or deceptive practices.
Email authentication
Verify your SPF, DKIM, and DMARC records are correctly configured. Improper authentication can contribute to blocking, as noted in discussions about Yahoo blocklists. Read our guide on DMARC, SPF, and DKIM.
Long-term prevention and monitoring
Addressing TSS04 errors is not a one-time fix, but an ongoing commitment to excellent email practices. Long-term prevention involves continuous monitoring of your email deliverability metrics and proactive list management.
Regularly monitor your complaint rates, bounce rates, and engagement metrics specifically for Verizon Media domains. Pay close attention to Yahoo's Postmaster Tools for insights into your sender reputation. Consistently maintaining low complaint rates (ideally below 0.1%) and high engagement will gradually improve your standing with Verizon Media's filters. If you are on an email blacklist or blocklist, this can also impact your deliverability, so regularly checking for these is also prudent.
Best practices for maintaining good sender reputation
Auditing sending practices: Regularly review your email sending practices across all departments or subsidiaries sharing an IP.
Segmenting lists: Segment your lists by engagement levels, prioritizing highly engaged subscribers for critical communications. Read more on how to increase email click-through rates.
Content optimization: Personalize email content and send frequency to match subscriber preferences.
Feedback loops: Sign up for all available feedback loops to quickly identify and remove users who mark your emails as spam.
By consistently applying these preventative measures, you can avoid future Verizon Media email blocking and TSS04 errors, ensuring a healthy and effective email program.
Views from the trenches
Best practices
Actively monitor engagement metrics for Verizon Media domains to detect early signs of declining interest or rising complaints.
Implement a strict double opt-in process for all new subscribers to ensure explicit consent.
Segment email lists based on engagement levels, prioritizing sends to your most active subscribers at Verizon Media.
Regularly clean your email lists to remove inactive or unengaged subscribers, reducing the risk of hitting spam traps.
Ensure your SPF and DKIM records are correctly configured and aligned to pass authentication checks.
Common pitfalls
Ignoring early signs of low engagement or minor TSS04 errors, which can escalate into full blocks.
Ramping up sending volume too quickly after a block, without rebuilding sender reputation gradually.
Failing to clean inactive subscribers from your lists, leading to higher complaint rates and spam trap hits.
Sending to purchased or unverified lists, which severely damages sender reputation and triggers blocks.
Assuming a temporary block will resolve itself without addressing the root cause of user complaints.
Expert tips
If multiple subsidiaries share an IP, a thorough audit of each entity's data sources is crucial to identify and fix permission issues.
Postmaster tools might not always provide clear answers for delisting, so focus on internal improvements.
Even a handful of TSS04 errors are a serious warning; tighten up your targeting immediately.
A period of rest is often needed after a block to allow your reputation to stabilize before attempting new campaigns.
The fundamental issue with TSS04 is that recipients do not want your mail, so improving content and targeting is paramount.
Marketer view
Marketer from Email Geeks says: The client's emails were blocked at Verizon Media, experiencing TSS04 errors intermittently before escalating to a 'bad connection' block. Postmaster responses were not helpful, even after submitting multiple tickets.
2019-11-14 - Email Geeks
Expert view
Expert from Email Geeks says: TSS04 is typically related to complaints, so review mail streams and list acquisition practices to reduce subscribers marking emails as spam.
2019-11-14 - Email Geeks
Moving forward
Resolving Verizon Media email blocking and TSS04 errors is a journey that requires patience and a deep understanding of email deliverability best practices. It's not just about getting off a blocklist, but about fundamentally improving your relationship with your subscribers and the ISPs.
By focusing on list quality, engagement, and consistent monitoring, you can overcome these challenges and achieve consistent inbox placement for your emails. Remember, a strong sender reputation is built on trust and positive user experience.
