Top Email Deliverability Solutions for Maximum Inbox Reach

You've spent hours, maybe even days, crafting the perfect email campaign. The copy is compelling, the design is clean, and your call to action is irresistible. You hit send, expecting a flood of opens and clicks, but all you get is silence. The hard truth is that if your emails aren't reaching the primary inbox, all that effort is wasted. This is where email deliverability solutions come in. They are the essential tools that diagnose why your messages get lost or sent to spam and provide the framework to fix it. This guide will walk you through everything you need to know, from understanding your sender reputation to choosing the right tools and implementing best practices.

Key Takeaways

Master the Technical Essentials First: Your deliverability efforts begin with a proper technical setup. Implementing authentication protocols like SPF, DKIM, and DMARC is a critical first step that verifies your identity to inbox providers and builds the trust required to stay out of the spam folder.
Proactively Manage Your Reputation and Lists: Your sender reputation is a direct result of your sending habits. Maintain it by regularly cleaning your email lists to prevent bounces and consistently monitoring performance metrics to address potential issues before they harm your standing with providers.
Make Engagement Your North Star: The best way to improve deliverability is to send emails people want to open. Focus on segmenting your audience and personalizing your content to drive high engagement, as this sends the strongest positive signal to inbox providers that your messages belong in the primary inbox.

What Are Email Deliverability Solutions?

You’ve spent hours crafting the perfect email campaign, building your list, and hitting send, only to wonder if anyone is actually seeing your message. If your open rates are low, there’s a good chance your emails are getting lost or sent straight to spam. Email deliverability solutions are tools designed to diagnose and fix these issues. Think of them as a support system for your outreach efforts, ensuring your carefully written emails successfully reach your audience’s inboxes.

These solutions analyze your campaigns to identify potential problems before they hurt your sender reputation. They help you understand why your emails might be getting flagged by spam filters and give you the insights needed to make improvements. For any business running high-volume campaigns, using a dedicated tool is essential for making sure your messages land where they’re supposed to.

What Goes Into Great Email Deliverability?

At its core, great email deliverability means a high percentage of your emails successfully land in the primary inbox. It’s not just about avoiding the spam folder; it’s about getting prime placement where your message will be seen. Several factors contribute to this, but two key elements are inbox placement and spam checking. Inbox placement tools show you exactly where your emails are going—the main inbox, the promotions tab, or the spam folder. A spam checker acts like a proofreader, scanning your email’s content and formatting to catch anything that might trigger spam filters. By paying attention to these details, you can significantly improve your chances of reaching your audience.

Why Email Deliverability Matters for Your Business

If your emails don't land in the main inbox, all the effort you put into writing them is wasted. Poor deliverability means lower open rates, fewer clicks, and ultimately, missed opportunities for connection and sales. Every email that goes to spam is a potential lead lost. Using a specialized email deliverability tool can dramatically improve how well your campaigns perform and help your messages avoid the spam folder. Investing in a dedicated email infrastructure protects your sender reputation and ensures your outreach efforts generate the return you expect. It’s the difference between shouting into the void and having a meaningful conversation with your audience.

A Breakdown of the Best Email Deliverability Solutions

Choosing the right email deliverability solution feels a lot like picking the right tool for a job—you need to know what you’re trying to build. Some tools are perfect for developers who need to test emails in a safe environment, while others are designed for marketers who need an all-in-one platform to monitor live campaigns. The key is to match the tool’s strengths to your specific goals, whether that’s scaling cold outreach or just making sure your transactional emails land in the right place. Let’s look at some of the top contenders and what they do best.

ScaledMail

If your goal is to send high-volume campaigns without sacrificing performance, ScaledMail is built for you. We provide a dedicated email infrastructure designed specifically for outreach at scale. Instead of a shared platform, you get custom-built systems that protect your sender reputation and ensure your emails actually reach the inbox. This is especially critical for cold email initiatives where every message counts. We handle the technical heavy lifting of warming up domains and managing IP addresses, so you can focus on crafting great campaigns that connect with your audience and drive results.

Glock Apps

Glock Apps is a fantastic and affordable tool for getting a clear picture of your overall deliverability. It tests where your emails are landing across a wide range of providers—like the inbox, spam folder, or even Gmail’s Promotions tab. The reports are easy to understand, making it a great choice if you want to check for spammy content, monitor your email authentication, and track your sender reputation without a steep learning curve. Just keep in mind that it uses a smaller test list, so the results are best used as a strong guide rather than an exact science.

Mailgun Optimize

For those who are more technically inclined, Mailgun Optimize offers a robust suite of deliverability tools. It’s especially useful if you’re already using Mailgun to send your emails. The platform helps you test inbox placement, validate email addresses, and monitor for spam traps. It also integrates well with Google Postmaster Tools to give you deeper insights into your domain and IP reputation. While it’s a powerful option, it’s geared more toward users who are comfortable with the technical side of email and doesn't specify placement in Gmail's Primary versus Promotions tabs.

Mailtrap

Think of Mailtrap as a safe sandbox for your emails. It’s designed for developers and QA teams who need to test and debug emails during the development process, long before they’re sent to actual customers. Mailtrap captures your test emails in a virtual inbox, allowing you to inspect HTML, check spam scores, and ensure everything renders perfectly without cluttering real inboxes. It’s not a tool for monitoring live campaign deliverability, but it’s an essential part of the process for making sure your emails are technically flawless from the start.

ZeroBounce

If you’re looking for a comprehensive, do-it-all solution, ZeroBounce is a strong contender. This platform packs a ton of features into one place, covering nearly every aspect of email deliverability from list verification to inbox placement testing and blacklist monitoring. It’s a great option for anyone who wants a single platform to manage everything, and their 24/7 live chat support is a huge plus. The pricing can be a bit complex, and verifying very large email lists can sometimes be slow, but it’s an incredibly thorough tool.

Unspam.email

Unspam.email is another excellent all-in-one tool that’s approachable for both beginners and experienced marketers. It simplifies the process of running a full check on your emails before you hit send. You can easily test for spam issues, check your deliverability across different providers, and get actionable advice for improving your campaigns. Like some other tools, it uses a smaller seed list for testing, so it’s best to view the results as a reliable snapshot to guide your strategy rather than a definitive report.

Must-Have Features for Better Deliverability

When you're evaluating email deliverability solutions or building your own tech stack, it can be tough to know what really matters. The good news is that the most effective tools share a core set of features designed to get your emails authenticated, tested, and monitored. Think of these as the non-negotiables for any serious email outreach program. Focusing on these key areas will give you the clarity and control needed to consistently land your messages in the inbox, where they belong. From verifying your identity with authentication protocols to cleaning your lists with validation systems, each feature plays a specific role in protecting your sender reputation and maximizing your reach.

Authentication Tools and Protocols

Think of email authentication as a digital ID card for your messages. Protocols like SPF, DKIM, and DMARC prove to inbox providers that your emails are legitimate and actually from you, not a spoofer. Setting up these records is a foundational step in building trust with providers like Gmail and Outlook. Without proper authentication, your emails are much more likely to be flagged as suspicious and sent straight to the spam folder. Most deliverability platforms help you implement these, but understanding the basics of email authentication is crucial for anyone sending high-volume campaigns. It’s the first and most important step toward a healthy sending reputation.

Spam Testing and Prevention

Before you hit send on a major campaign, wouldn't you want to know if it looks like spam? That's exactly what a spam checker does. This feature scans your email content, subject line, and even the HTML code to identify potential red flags that could trigger spam filters. It might catch spammy-sounding phrases, poor image-to-text ratios, or broken links. By running a test before you send, you can fix issues proactively instead of reacting to poor deliverability after the fact. It’s an essential quality check that helps ensure your carefully crafted message doesn't get filtered out before your audience ever sees it.

Inbox Placement Testing

A "delivered" status doesn't always mean your email landed in the main inbox. It could have been routed to the promotions tab, a secondary folder, or the spam folder. Inbox placement testing gives you the real story. These tools use a seed list of email addresses from various providers to show you exactly where your campaigns are landing. This insight is far more valuable than a simple delivery receipt because it tells you if your audience is actually seeing your message. If you find your emails are consistently hitting the spam folder, you know you have a deliverability problem to address.

Blacklist Monitoring

Email blacklists are lists of IP addresses and domains that have been identified as sources of spam. If your sending domain or IP ends up on one, your emails will be blocked by a large number of providers, and your deliverability will plummet. Blacklist monitoring tools automatically check major blacklists and alert you if you’ve been listed. This allows you to act quickly to identify the cause—like a compromised account or a problematic campaign—and begin the delisting process. Regular monitoring is critical because you often won't know you're on a blacklist until your delivery rates suddenly drop off a cliff.

Analytics and Reporting

You can't improve what you don't measure. Strong analytics and reporting are the backbone of any successful email program. Beyond basic open and click rates, a good deliverability solution provides detailed reports on bounce rates (hard and soft), complaint rates, and delivery rates across different inbox providers. These metrics are your feedback loop. They tell you how recipients and their email services are responding to your messages. A sudden spike in soft bounces or spam complaints, for example, is an early warning sign that you need to investigate a potential issue with your content, list, or reputation.

Reputation Monitoring Tools

Your sender reputation is the score that inbox providers use to judge how trustworthy you are. This score is tied to your sending domain and IP address and is influenced by factors like engagement levels, bounce rates, and spam complaints. Reputation monitoring tools track this score over time, giving you a clear view of your standing with major providers. Some services, like the Mailgun Optimize suite, provide a dashboard to watch your reputation and identify trends. If your score starts to dip, you can take corrective action before it leads to widespread deliverability problems.

Email Validation Systems

Sending emails to invalid or non-existent addresses results in hard bounces, which is a major red flag to inbox providers and can quickly damage your sender reputation. An email validation system cleans your list before you send. It checks for typos, disposable addresses, and other risky contacts that are likely to bounce. Integrating an email validation service into your workflow is one of the most effective ways to maintain good list hygiene. A clean list leads to fewer bounces, better engagement metrics, and a stronger sender reputation, all of which are essential for great deliverability.

How to Monitor Your Email Performance

Sending an email campaign is just the first step. The real work begins once you hit send, because what happens next determines your future success. Monitoring your email performance isn’t about vanity metrics; it’s about understanding how inbox providers and recipients perceive your emails. Consistent tracking helps you catch deliverability issues before they snowball into a damaged sender reputation that’s tough to repair.

Think of it as a health check for your email program. By keeping a close eye on key data points, you can see what’s working, what isn’t, and make informed adjustments. Are your emails landing in the inbox? Are people actually opening them? Are you getting too many spam complaints? Answering these questions requires a commitment to monitoring. Specialized email deliverability tools can help you diagnose why your emails aren’t reaching the inbox by testing placement, flagging technical problems, and giving you the insights needed to protect your reputation. With the right approach, you can move from simply sending emails to strategically managing a high-performing outreach channel.

Key Metrics You Need to Track

To get a clear picture of your email performance, you need to track a few core metrics. Start with the basics: open rate, click-through rate, and unsubscribe rate. These show how engaged your audience is. But for deliverability, you need to dig deeper. Your delivery rate tells you the percentage of emails that were successfully delivered to recipients' mail servers. The bounce rate shows how many failed. Pay close attention to hard bounces (invalid addresses) versus soft bounces (temporary issues). Finally, the spam complaint rate is critical. Even a small number of complaints can seriously harm your sender reputation. Keeping an eye on these numbers helps you see what’s working and what needs to be fixed to improve delivery.

What is Sender Reputation?

Your sender reputation is essentially your trustworthiness score in the eyes of internet service providers (ISPs) like Gmail and Outlook. A high score means your emails are more likely to land in the inbox, while a low score sends you straight to the spam folder. This score isn't random; it’s built on your sending history. ISPs look at factors like how many spam complaints you receive, whether your IP address is on any blacklists, how many of your emails bounce, and if your recipients are engaging with your content. Maintaining a positive sender reputation is fundamental to successful email outreach, as it directly influences whether your messages get delivered.

How to Measure Engagement Rates

Engagement rates are your direct line of feedback from both your audience and their email providers. When people open, click, and reply to your emails, it signals to providers like Gmail that your content is valuable and wanted. High engagement can significantly improve your inbox placement. Key metrics to watch are your open rate (who’s opening your emails) and your click-through rate (who’s taking action on your content). A low open rate might mean your subject lines aren't compelling or you're landing in spam. A low click-through rate could indicate your call-to-action or offer isn't resonating. Consistently low engagement is a red flag that can hurt your sender reputation over time.

How to Analyze Delivery Reports

Your delivery reports are where the story of your campaign unfolds. These reports, provided by your email platform, give you a detailed breakdown of your performance metrics. Instead of just glancing at the numbers, use them to identify patterns. For example, are you seeing a high bounce rate from a specific domain, like @yahoo.com? This could point to an issue with how that particular ISP views your emails. Using a dedicated email deliverability service can give you even deeper insights, showing you exactly where your emails are landing—the inbox, the promotions tab, or the spam folder. Analyzing these reports helps you move from guessing to knowing what’s wrong.

Set Your Performance Benchmarks

There’s no universal "perfect" open rate or click-through rate. What matters is what’s normal for you. To effectively monitor your performance, you need to establish your own benchmarks. Start by tracking your key metrics for every campaign. After a few sends, you’ll have a baseline average for your open, click, bounce, and complaint rates. This baseline becomes your standard. If you see a sudden, significant drop in your open rate or a spike in spam complaints compared to your average, you’ll know immediately that something is wrong. This proactive approach allows you to identify and fix deliverability issues before they cause lasting damage to your reputation.

How to Solve Common Deliverability Problems

Even the most carefully crafted email campaigns can run into trouble. If you notice your open rates dropping or hear that your messages are landing in spam, it’s time to do some troubleshooting. Most deliverability issues come down to a few common culprits, and thankfully, they all have straightforward solutions. Think of this as your go-to guide for diagnosing and fixing the problems that are holding your outreach back. By addressing these issues head-on, you can get your emails back into the inbox where they belong and start seeing the results you want. From technical setups like authentication to strategic moves like cleaning your email list, each step plays a crucial role in building a strong sender reputation. We'll walk through the most frequent problems one by one and give you the exact, actionable steps you can take to solve them for good.

Fix Authentication Setup Issues

If your emails aren't authenticated, you're basically showing up to the inbox party without an ID. Email authentication protocols like SPF, DKIM, and DMARC are the technical standards that prove your emails are actually from you. They act as a digital signature, telling receiving servers that you’re a legitimate sender, not a spoofer or phisher. Setting them up correctly is one of the most critical first steps for building trust with providers like Gmail and Outlook. Without proper email authentication, your messages are far more likely to be flagged as suspicious and sent straight to the spam folder, no matter how great your content is.

Improve a Poor Sender Reputation

Your sender reputation is like a credit score for your email domain. Internet Service Providers (ISPs) track how recipients interact with your emails—do they open them, click links, or mark them as spam? All of this data feeds into your reputation. A low score tells ISPs that your emails might be unwanted, making it harder for future campaigns to reach the inbox. You can check your sender score using various online tools to see where you stand. If your reputation needs work, focus on sending high-quality, engaging content to a clean email list and gradually warming up your domain to rebuild that trust with ISPs over time.

Get Out of the Spam Folder

Landing in the spam folder is often a sign that your audience isn't finding your content relevant, or worse, they feel trapped. The single best way to avoid this is by making it incredibly easy for people to unsubscribe. A clear, one-click unsubscribe link at the bottom of every email is non-negotiable. When someone can’t easily opt out, they’re far more likely to hit the spam button out of frustration. That spam complaint is a major red flag for ISPs and does significantly more damage to your sender reputation than a simple unsubscribe ever could. Respecting your audience's choice is key to maintaining a healthy sending practice and staying in the inbox.

Deal with Blacklisting Problems

Getting blacklisted means your domain or IP address has been flagged for sending spam. When this happens, your emails will be blocked outright by servers that use that specific blacklist, bringing your outreach to a complete halt. It’s a serious issue, so you should regularly check if your domain is on any major blacklists using monitoring tools like MXToolbox. If you find yourself on a list, the first step is to identify and fix the root cause—it could be a compromised account, a bad email list, or sudden volume spikes. Once you’ve resolved the issue, you can contact the blacklist administrator to request removal.

Reduce High Bounce Rates

A "bounce" happens when an email can't be delivered to a recipient's address. High bounce rates are a major red flag for ISPs because they suggest you aren't managing your email lists properly. Sending to a long list of invalid or non-existent addresses looks like spammy behavior and can quickly damage your sender reputation. The solution is proactive list hygiene. Before sending a campaign, use an email validation service to clean your list. These tools check for typos, outdated domains, and known spam traps, allowing you to remove problematic addresses before they can cause a bounce.

Turn Around Low Engagement Rates

ISPs don't just look at negative signals like spam complaints; they also pay close attention to positive ones like opens and clicks. If your engagement rates are consistently low, it tells providers that your audience isn't interested in what you're sending. This can cause them to start filtering your messages into the spam folder. To fix this, focus on sending more relevant content. The best way to do this is through email list segmentation. Group your subscribers based on their interests, behavior, or demographics, and tailor your messages to each specific group. Personalized content gets better engagement, which sends positive signals to ISPs.

Your Implementation Checklist and Best Practices

Having the right email deliverability solution is a huge step forward, but the tools themselves are only part of the equation. To truly land in the inbox consistently, you need to pair that powerful infrastructure with solid sending practices. Think of it like having a high-performance race car—it won't win any races if you don't know how to drive it properly. The good news is that these practices aren't complicated. They’re all about building and maintaining trust with internet service providers (ISPs) like Google and Microsoft.

This checklist covers the essential habits that separate the pros from the spammers. By following these steps, you're showing ISPs that you're a legitimate sender who provides value to your recipients. This isn't a one-time setup; it's an ongoing process of managing your lists, warming up your domains, and monitoring your performance. Committing to these best practices will protect your sender reputation and ensure your carefully crafted messages reach their intended audience. If you're ready to build a foundation for long-term success, our team at ScaledMail can help you get started with the right infrastructure and strategy.

Set Up Authentication Protocols

First things first: you need to prove you are who you say you are. Email authentication protocols like SPF, DKIM, and DMARC are the way you do this. Think of them as a digital ID card for your domain. They verify to receiving email servers that your message is legitimate and hasn't been forged by a phisher or spammer. Setting these up is a non-negotiable first step. It’s a technical but critical process that tells ISPs you’re a trustworthy sender, which is the absolute foundation of good deliverability. Without proper email authentication, your chances of hitting the spam folder increase dramatically.

Manage Your Email Lists

Your email list is your most valuable asset, so treat it that way. Sending emails to invalid, old, or unengaged addresses is a fast track to a poor sender reputation. High bounce rates and low engagement signal to ISPs that you aren't paying attention to your audience. That's why regular list hygiene is so important. Before you send a single email, use a validation service to scrub your list of invalid addresses. On an ongoing basis, make it a habit to remove subscribers who haven't opened your emails in several months. A smaller, highly engaged list will always outperform a massive, unmanaged one.

Warm Up Your Domain

You can't go from zero to sending 10,000 emails a day with a new domain or IP address. Trying to do so is a major red flag for ISPs and will likely get you blocked immediately. Instead, you need to warm up your domain. This process involves starting with a very low sending volume and gradually increasing it over several weeks. This slow and steady approach builds a positive sending history and shows ISPs that you're a legitimate sender, not a spammer blasting out emails. A proper domain warm-up is the only way to establish a good reputation from scratch.

Monitor Your Performance

Email deliverability isn't a "set it and forget it" activity. You need to actively monitor your performance to catch problems before they spiral out of control. Keep a close eye on your key metrics: open rates, click-through rates, bounce rates, and spam complaint rates. These numbers tell a story about how recipients and ISPs perceive your emails. A sudden drop in open rates or a spike in bounces could indicate a problem with your sender reputation. Tools like Google Postmaster Tools can give you direct insight into how Gmail is handling your emails and the health of your domain reputation.

Perform Regular Maintenance

Just like a car, your email program needs regular check-ups to keep it running smoothly. A key part of this maintenance is checking to see if your domain or IP has landed on any blacklists. A blacklist is a real-time database of domains and IPs that have been reported for sending spam. Being on one can completely halt your email delivery. Use a free tool to check for blacklistings regularly. If you find yourself on a list, you'll need to identify and fix the root cause of the problem (like a compromised account or poor list hygiene) before you can request to be removed.

Advanced Techniques to Optimize Deliverability

Once you’ve mastered the fundamentals of email deliverability, it’s time to fine-tune your approach. Think of it like going from a good cook to a great chef—it’s all in the details. These advanced strategies are about being proactive, data-driven, and deeply in tune with your audience. By implementing these techniques, you can move beyond simply avoiding the spam folder and start building a powerful, resilient sending infrastructure that consistently reaches the inbox and drives results.

Advanced Reputation Management Strategies

Your sender reputation isn't static; it needs constant attention. Advanced reputation management involves using dedicated tools to get a clear picture of how mailbox providers see you. These services go beyond basic monitoring to test exactly where your emails are landing—inbox, promotions, or spam—and diagnose the technical issues that might be holding you back. This proactive approach helps you spot potential problems, like a misconfigured DNS record or an accidental listing on a small blocklist, before they escalate. By regularly checking your reputation, you can maintain a strong, positive sending history that keeps your email outreach effective.

Master Your List Hygiene

A clean email list is the foundation of great deliverability. Beyond just removing hard bounces, mastering list hygiene means regularly scrubbing for inactive subscribers, correcting typos in email addresses, and identifying potential spam traps. It also involves keeping a close eye on email blocklists. If your domain or IP lands on a blocklist, your delivery rates will plummet. Use monitoring tools to get alerts if you’re ever listed. If it happens, act quickly to identify the root cause—like a sudden spike in spam complaints—fix the issue, and follow the blocklist’s instructions to request removal. This diligent maintenance ensures you’re only sending to people who want to hear from you.

Optimize for Better Engagement

High engagement is one of the strongest signals you can send to mailbox providers that your emails are valuable. The best way to achieve this is by sending relevant content, and that starts with segmentation. Instead of sending the same message to your entire list, divide your audience into smaller groups based on their interests, location, or past behavior. For example, you could create segments for new leads, loyal customers, or users who haven't engaged in a while. By tailoring your messaging to each group, you make your emails feel more personal and useful, which naturally leads to more opens and clicks. This targeted approach shows providers that your recipients welcome your emails.

Create a Framework for Testing and Analysis

The most successful email marketers don't guess what works—they test it. Building a consistent framework for testing and analysis is key to long-term deliverability success. Start by A/B testing one variable at a time, whether it’s your subject line, call to action, or send time. Track the results carefully to see what resonates with your audience. This creates a powerful feedback loop where every campaign provides insights for the next one. Using a platform with robust analytics allows you to monitor your campaigns and make data-backed decisions that continuously improve your performance and strengthen your sender reputation over time.

The Critical Metrics That Define Success

To truly understand your deliverability, you need to look beyond open rates. While opens are a good starting point, they don’t tell the whole story. Pay close attention to your click-through rate, conversion rate, and reply rate, as these show that your audience is actively engaging with your content. Equally important are the negative metrics: bounce rates, unsubscribe rates, and spam complaint rates. A high bounce rate could signal a problem with your list hygiene, while a spike in spam complaints is a major red flag for your sender reputation. Tracking these key metrics gives you a complete view of your email health and helps you pinpoint exactly where you need to make improvements.

Frequently Asked Questions

What's the single most important thing I can do to improve my email deliverability right now? Before you do anything else, make sure your email authentication is set up correctly. This means getting your SPF, DKIM, and DMARC records in order. Think of these as your domain's official ID card. They prove to providers like Gmail and Outlook that your emails are legitimate and not from a spammer impersonating you. It’s a technical but foundational step that builds immediate trust and has a massive impact on whether you land in the inbox or the spam folder.

How can I tell if I have a deliverability problem in the first place? The most obvious signs are a steady decline in your open rates or a sudden spike in your bounce rates. If your open rate is consistently below 10-15%, that's a red flag. Another clear indicator is when you hear directly from prospects or customers that your emails are landing in their spam folders. Don't just rely on the "delivered" metric in your email platform; that number doesn't tell you if your message actually made it to the primary inbox where people will see it.

What’s the difference between a dedicated infrastructure like ScaledMail and a testing tool? Think of it this way: a testing tool like Glock Apps is like getting a diagnostic check on your car. It tells you what’s wrong—for example, that your emails are going to spam. A dedicated infrastructure like ScaledMail is the high-performance engine itself. It’s the system you use to send your emails that is built from the ground up to protect your sender reputation and ensure high performance, which helps prevent those problems from happening in the first place, especially when you're sending a high volume of emails.

I've been blacklisted. Is my domain ruined forever? No, it’s definitely not ruined, but you do need to act quickly. Getting blacklisted is a serious problem, but it's almost always fixable. The first step is to stop sending and figure out why you were listed. It could be a bad email list, a sudden spike in volume, or even a compromised account. Once you've identified and fixed the root cause, you can follow that specific blacklist's process to request removal. It takes some work, but a domain can absolutely recover.

Is it better to focus on cleaning my existing list or getting new subscribers? Always focus on cleaning your existing list first. Sending emails to a large, unmanaged list full of invalid or unengaged contacts will damage your sender reputation. This makes it harder for all of your emails—even those to new, interested subscribers—to reach the inbox. A smaller, highly engaged list is far more valuable. Once you have a healthy, clean list and a strong reputation, your efforts to attract new subscribers will be much more successful.