What should I do if almost 100% of my emails are bouncing after a block?

If nearly all your emails are bouncing, the immediate step is to halt all sending. Continuing to send only worsens your reputation. Then, focus on a thorough list cleanup, removing inactive subscribers and identifying any problematic acquisition sources. After cleaning, apply for delisting from relevant blocklists and postmasters, and slowly begin a re-warmup process with only your most engaged subscribers.

What do bounce codes like 421 4.7.0 TSS04 mean?

Bounce codes like 421 4.7.0 TSS04 from Verizon (or similar from other providers) generally indicate that your messages are being temporarily deferred or rejected due to a high volume of user complaints or other negative signals. This suggests that your emails have likely been landing in spam folders or generating complaints for some time, leading to a severe reputation downgrade.

Why would a sender reputation problem appear to come out of nowhere?

Sender reputation can deteriorate rapidly due to sudden spikes in spam complaints, high bounce rates (especially hard bounces), or hitting a spam trap . Even linking to a compromised or spammy domain within your email content can trigger immediate blocks. While it might seem sudden from your data, reputation issues often build over time before leading to a hard block.

Can sending transactional emails help rebuild a marketing IP's reputation?

Yes, it is possible. If your marketing IP is fully blocked, temporarily routing a small volume of transactional emails through it can help. Users often seek out transactional emails (e.g., password resets) and their positive engagement (opens, clicks) can send strong, positive signals to inbox providers, aiding in the rehabilitation of your IP's reputation.

How to rehabilitate sender reputation with inbox providers after being blocked? - Sender reputation - Email deliverability - Knowledge base

Getting blocked by an inbox provider is a frustrating experience for any email sender. One day your emails are delivering, and the next, you see a sudden, drastic drop in deliverability, often accompanied by bounce messages indicating a block. This isn't just a temporary hiccup, it's a clear signal that the inbox provider (like

Yahoo or

Gmail) has lost trust in your sending practices and is actively preventing your mail from reaching recipients. Rehabilitating your sender reputation after such an incident is challenging, but it's crucial for your email program's long-term health.

The immediate impact of being blocked is obvious: your campaigns aren't reaching their intended audience. What's less obvious is the underlying cause, which often stems from a prolonged period of poor sending habits or a sudden, severe issue that triggered the provider's defenses. It's not uncommon for senders to experience bounce codes like 421 4.7.0 TSS04, indicating temporary deferrals due to user complaints. This means that a significant portion of your audience has been marking your emails as spam, even if you weren't immediately aware of it.

Recovering from this state requires a strategic and disciplined approach. You can't just keep sending and hope for the best; that will only deepen the hole you're in. The goal is to systematically identify and address the root causes of the block, demonstrate improved sending behavior to inbox providers, and slowly rebuild their trust in your domain and IP address. This guide outlines the essential steps I recommend to help you regain good standing and ensure your emails reach the inbox.

Immediate actions after a block

When you encounter a widespread block, the first and most critical step is to halt all email sending on the affected domain or IP. Continuing to send emails when they are being rejected or routed directly to spam folders only exacerbates the problem. Inbox providers monitor every attempt you make, and persistent sending in the face of rejections will further damage your reputation, making recovery significantly harder. Think of it as hitting a wall, you need to stop and assess the damage, not keep pushing forward.

Once sending has ceased, the next immediate action is a thorough cleanup of your subscriber list. The most likely reason for a block, especially one due to user complaints, is that a large portion of your audience no longer wants your emails. Focus on identifying and removing inactive subscribers. I typically recommend purging contacts who haven't engaged with your emails (opened or clicked) in the last three to six months. This may seem drastic, but sending to unengaged users signals to inbox providers that your list quality is poor, leading to more complaints and blocks.

Beyond inactivity, scrutinize your list acquisition methods. Are there any questionable sources? Purchased lists or scraped addresses are notorious for causing rapid reputation decline. If you've recently integrated new lead sources, pause them and review their quality. This also includes looking at your content itself. Sometimes, an unexpected block can be linked to domains or specific content within your email that is perceived negatively by filters, even if they aren't explicit links.

Strengthening authentication and monitoring

Email authentication protocols like SPF, DKIM, and DMARC are foundational to establishing and maintaining a strong sender reputation. These records verify that your emails are legitimately coming from your domain, reducing the likelihood of them being flagged as spam or spoofed. If your domain or IP was blocklisted, verifying the proper configuration of these records is a non-negotiable step in your rehabilitation process.

For

Microsoft (Outlook.com) and Gmail, having a DMARC policy at p=quarantine or p=reject is now a mandatory requirement for bulk senders. If you are not compliant, your emails will be rejected. This is a baseline requirement, and without it, your rehabilitation efforts will be futile. You can use a free DMARC record generator to get started, but ensure proper configuration and monitoring.

Beyond setup, ongoing blocklist monitoring is essential. While a major inbox provider block is distinct from being listed on a public blacklist (blocklist), these lists are indicators of broader reputation issues. If your IP or domain appears on common blacklists, it further confirms a negative reputation and can impact deliverability across various providers. Regularly checking these lists and promptly requesting delisting is part of a proactive reputation management strategy.

Gradual re-engagement and appeals

After a block and thorough list cleanup, you cannot simply resume sending at your previous volume. You must implement a careful warm-up strategy, similar to warming up a new IP address. The core principle is to send very small volumes of email to your most engaged subscribers first. These are the contacts who consistently open and click your emails. Their positive interactions will help send positive signals to the inbox providers, indicating that your mail is wanted and valued.

Gradually increase your sending volume to this highly engaged segment over several days or weeks, depending on the severity of the block and the provider. Only when you see consistent inboxing for this group should you slowly expand to slightly less engaged segments, always monitoring your deliverability rates closely. This cautious approach helps rebuild your reputation incrementally. Remember that recovering reputation takes time, often 30-45 days or more, depending on the changes you implement.

For specific inbox providers, you may also need to appeal directly to their postmaster teams. For example, for

AOL, which is now part of the Verizon Media Group, you would visit their postmaster site. When you submit a delisting request, clearly explain the steps you've taken to identify and resolve the issue, such as stopping sends and cleaning your list. Transparency and demonstrated corrective action are key to a successful appeal.

If your main sending IP is dedicated to marketing, consider if temporarily routing a small volume of transactional emails (like password resets or account notifications) through that IP is feasible. Users often actively look for transactional emails, even in spam folders, and their positive engagement (opening, clicking) can provide strong positive signals to inbox providers, aiding in rehabilitation. This is a nuanced approach, and not always possible, but can be effective.

Understanding the root causes of reputation damage

The Challenge: Recovering from a hard block

Full block: Nearly 100% of emails are bounced, often with codes like 421 4.7.0 TSS04 indicating temporary deferral due to user complaints.
No mail ingress: Traditional strategies like re-engagement campaigns are difficult when mail isn't getting through.
Sudden appearance: The issue seems to appear suddenly, although it often has underlying causes from prior sending behavior.

Understanding why your domain was put on a blocklist (or blocklisted by a major inbox provider) is the first step toward recovery. Often, it's a culmination of various factors, not just a single incident. High bounce rates, low engagement, and a significant number of spam complaints are primary culprits. Inbox providers track these metrics closely, building a reputation score for your sending IP and domain. When this score drops below a certain threshold, blocks occur.

Factors influencing your sender reputation include spam complaint rates, bounce rates (especially hard bounces), unsubscription rates, and engagement metrics like open and click-through rates. Spam traps are another significant risk; hitting one can severely damage your reputation. Regularly reviewing your email analytics and troubleshooting deliverability issues can help you catch problems before they escalate to a full block.

The content of your emails also plays a role. Certain keywords, excessive images, poor HTML, or embedded links to compromised domains can trigger spam filters. Even if the links aren't explicitly malicious, if they are associated with spammy content elsewhere on the internet, it can impact your reputation. A deep dive into your recent email content, especially those sent just before the block, is essential.

Rebuilding trust through consistent, positive sending

Once you've stopped sending, cleaned your list, and fortified your authentication, the next phase is to slowly and methodically reintroduce your mail flow. This isn't a quick fix, and patience is key. Inbox providers want to see consistent, positive sending behavior over time. They won't instantly trust you again, especially after a severe block. The recovery timeline can vary, but typically it takes weeks or even months to rebuild a severely damaged reputation.

During this period, focus intently on sending only to your most active and engaged subscribers. This means segmenting your list to include only those who have opened or clicked an email very recently. As you observe consistent positive deliverability to this segment, you can incrementally increase the volume and gradually broaden your audience to slightly less engaged users. This careful ramp-up is critical for demonstrating consistent positive engagement to inbox providers.

Beyond the technical fixes, improving content quality is paramount. Ensure your emails provide genuine value, are relevant to your audience, and encourage positive engagement. Avoid spammy keywords, excessive images, or deceptive subject lines. Consider implementing a double opt-in process for new subscribers to ensure you're only adding highly engaged individuals to your list, reducing future complaint rates. The more engagement you can generate, the faster your reputation will improve.

Views from the trenches

Best practices

Always halt sending immediately when a severe block occurs to prevent further reputation damage.

Thoroughly clean your email lists, removing all unengaged or inactive subscribers.

Ensure all email authentication protocols like SPF, DKIM, and DMARC are correctly configured.

Start re-sending emails at very low volumes to your most engaged audience segments.

Common pitfalls

Continuing to send emails after being blocked, which worsens the sender's reputation.

Failing to adequately clean subscriber lists, leading to continued low engagement and complaints.

Neglecting to implement or verify proper email authentication, especially DMARC policies.

Attempting to send at high volumes too soon after a block, causing further rejections.

Expert tips

Consider temporarily sending transactional emails through the blocked IP to generate positive engagement signals.

Investigate any external domains or links used in your email content, as these can trigger blocks.

Regularly appeal to postmaster teams after implementing corrective measures to request delisting.

Understand that reputation recovery is a gradual process that requires consistent monitoring and adjustments.

Marketer view

Marketer from Email Geeks says that determining if an IP solely handles marketing or also transactional emails is crucial, as transactional mail can help with recovery.

2020-02-21 - Email Geeks

Expert view

Expert from Email Geeks says that when experiencing a full block, the first step is to immediately stop sending because providers still monitor every attempt and its content.

2020-02-21 - Email Geeks

The path to restored deliverability

Recovering your sender reputation after being blocklisted by an inbox provider is a comprehensive process that demands immediate action, rigorous clean-up, and a disciplined approach to re-engagement. It's not about finding a quick workaround, but rather demonstrating a genuine commitment to good sending practices. By stopping sends, thoroughly cleaning your lists, ensuring robust email authentication, and slowly re-warming your sending volume with highly engaged users, you can systematically rebuild trust.

Consistency and patience are your most valuable assets in this journey. It can take time, but a sustained effort will eventually lead to improved inbox placement and a healthier email program. Continuously monitor your deliverability metrics, respond to postmaster feedback, and adapt your strategies based on provider responses. This proactive and diligent approach is the only way to ensure long-term success in email deliverability.