Email Blacklist Check: Expert Guide to Identify Blacklisted Emails

Email is the most reliable source of marketing ROI – granting up to $42 for every dollar spent.

That email revenue benchmark is only possible if your emails reach subscriber inboxes. Numerous factors, like bounce rate and engagement, can negatively impact your inbox placement. But none may be so impactful as email blacklists or blocklists.

If you find yourself asking: is my email blacklisted? Your company email domain may already be at risk.

This expert guide will explain how to tell if your email has been blacklisted and what you can do to fix it.

An email blacklist is a database of IP addresses and email domains that have a history of sending spam. The purpose of an email blacklist is to filter out spam senders and direct their messages where they belong – to the junk folder. In most cases, though, emails from blacklisted senders get blocked altogether.

• Email blacklists are created and maintained by mailbox providers (like Gmail, Outlook, Yahoo, and others) and independent anti-spam organizations. The goal of these entities is to provide people with a safe and relevant experience in their inboxes.
• There are more than 300 email blacklists. Running regular email blacklist checks is the fastest way to detect if your emails are going to spam or are not getting delivered. Also, there are several types of blacklists: public, private, internal, IP-based, domain-based, and blacklists that include both IP and domains.
• The technical term for email blacklists is Domain Name System-Based Blackhole Lists (DNSBL) or Real-Time Blackhole Lists (RBL). As the latter suggests, blacklists are updated in real time, which makes it challenging for senders to know when their IPs or domains have been flagged.

We’ll explore these topics below to give you a full picture of how blocklists work, how they affect you, and how you can tell that your IP or domain may be blacklisted.

Decreased deliverability and engagement

One of the first signs that your email is blacklisted is a decrease in your email deliverability and engagement. Email blacklists help mailbox providers intercept and trap spam in the spam folder. Therefore, having your IP or domain on one of these lists impairs your ability to reach the inbox.

Email expert and Mailchimp Pro Partner Emily Ryan, founder of Westfield Creative, says: “However, when their metrics drop, many marketers automatically assume people don’t care about their content anymore.”

The email pro adds: “We care so much about creating engaging content that we sometimes tend to overlook technical issues like this. If you haven’t changed your content and if your email list is valid and active, check your blacklist status. Nobody wants to end up on one, but being aware is the first step to getting off that list.“

Rejected or bounced emails

ZeroBounce SMTP Deliverability Specialist Radu Pasarica suggests that bounced emails can indicate that your email has been blacklisted.

Expert Tip - If you unexpectedly bounce emails or notice a high email bounce rate on your campaigns, use a blacklist checker to see if you’ve been listed.

Blocked emails

Email servers can cause hard bounces by blocking your domain. However, this differs from a typical hard bounce, which often occurs when you email an invalid address. A blocking is deliberate and is a telltale sign that there is an issue with your email domain or IP address.

Pasarica adds additional input on the matter:

Expert Tip – Pay attention to the error message attached to a bounced email. If you receive a specific type of bounce-back error message (e.g., 550 5.7.1 Message blocked), it means that the recipient server has permanently blocked you. A permanent block may indicate that your domain or IP has been blacklisted.

Sudden Drop in Delivery Rates

A decrease in your email delivery rate goes hand-in-hand with an increased bounce rate.

Our SMTP specialist Pasarica adds one final tip:

Expert Tip – Never assume that a new campaign’s metrics will be similar to the last. After sending your campaign at the scheduled time, check your delivery and bounce rate. If you notice an unusual change from your normal metrics, consult a blacklist checker immediately.

All email blacklists operate under the same goal: to keep email safe by preventing spam from making it to user inboxes. But there are different kinds of email blacklists, and understanding them gives you more knowledge on how to get delisted.

Public email blacklists

These blacklists are free for you to consult. They are public, and any ISP can use them, so they’re the first you should consider when performing a domain or IP blacklist check.

Private email blacklists

Anti-spam organizations create, maintain, and provide these types of blacklists as a service to larger entities such as ISPs and mailbox providers. The only way to check these lists is by using inbox testing tools.

Internal email blacklists

Email providers like Google, Yahoo, or Outlook maintain their email blacklists. Getting on an internal blacklist of a popular provider is highly detrimental as it blocks your access to a large segment of your prospects. However, you can monitor these lists with inbox testing tools, too.

Another fact to keep in mind is that email blacklists can be:

• IP-based: They aggregate mail server IPs associated with spam.
• Domain-based: They group domains known to send spam
• IP and domain-based: These lists track a combination of IP and domains with a spam history.

Some of the most prominent email blacklists include:

• Spamhaus Block List
• SenderScore
• FortiGuard
• Composing Blocking List
• Barracuda
• Cyren
• SURBL Blacklist
• Spamcop
• Invaluement

A fast and easy way to run an IP blacklist check is by using multirbl.valli.org. It runs a complete check for your mail server IP to determine its status.

If you want to check both your domain and IP blacklist status, consider ZeroBounce’s free Blacklist Checker. It checks against 200+ blacklists. In addition, if you scan your domain with this tool, it will provide you with every IP address associated with that domain so that you can easily check those as well.

Do you suspect that your email domain or IP could be on a blacklist – or several?

Siva Devaki, Founder and Co-CEO of MassMailer has this to say about fixing a blacklisted email domain:

“It’s not hard to get off an email blacklist. However, depending on the organization you’re working with to delist your domain or IP, at times, it may be time-consuming or challenging.”

He continues, “My advice is to get all the information ready to provide the correct justification to the delisting organization so that they can approve your request. You want to be genuine in your response, as they will certainly monitor your domain/IP for a few more weeks, even after the delisting takes place. At the end of the day, the rule of thumb for good email deliverability is not to spam.”

Here’s the step-by-step process to fix an email domain or IP that’s blacklisted.

Step 1 - Identify the email blacklist

There are two methods for determining if your domain or IP is on an email blacklist:

• Use a blacklist checker – This tool allows you to look up your domain or IP address. The results will reveal if either is on a blacklist.
• Use a blacklist monitor (recommended) – Due to the consequence severity, proactive monitoring against email blacklists is necessary. Authenticate the domain or IP you wish to monitor, and the tool will automatically notify you when a blacklisting occurs.

ZeroBounce’s Blacklist Monitor runs email blacklist checks in real time for a domain/subdomain as well as IPv4 and IPv6 addresses. It compares both against more than 200 email blacklists.

After you set your email domain or IP, enter an email address. The monitor will send an automated notification if either is found on an email blacklist. No additional actions are required.

Step 2 – Contact the blacklist service

If you receive a notification that your domain or IP is blacklisted, consult your blacklist monitor.

The ZeroBounce Blacklist Monitor will send a notification that lists and links to any discovered blacklists. Here’s an example of the notification:

For each email blacklist included, follow the provided links to contact each. Each service has a unique protocol to follow, so be certain to follow up quickly to determine why your domain or IP was added.

Step 3 – Resolve the underlying issue

After contacting the blacklist service, they should provide you with feedback on what you need to resolve before you may be removed.

It’s critical to follow these instructions closely. In addition, take care to document the actions taken to include in your removal request. Show a good faith effort to help the provider prevent spam, and they will reciprocate by removing your blacklisted domain or IP.

Pro Tip – After you are removed from an email blacklist, the service may continue to monitor your domain or IP address. Not only should you be proactive with a blacklist monitor, but it’s important to regularly audit your email domain for configuration or security issues with regular campaign tracking, DMARC Monitoring, and email server testing.

While getting off an email blacklist can be a nuisance, avoiding one in the first place isn’t hard if you send emails responsibly.

Here are important rules to follow to avoid them.

Build your own email list

Buying an email database may sound tempting, but refrain from doing that if you want to stay off email blacklists. When you purchase or rent an email list, you’re often buying recycled lists that have been sold hundreds or thousands of times. They also typically contain outdated, invalid emails and spam traps.

Additionally, the real users on those lists didn’t opt into your emails. They will report you as spam, which is a quick way to get blacklisted.

Set up double opt-in

Use a double opt-in confirmation to ensure you have consent from every new subscriber. Here’s how to do it:

1. Create an autoresponder message that triggers whenever your newsletter signup form receives a new subscription. Most ESPs offer this as a built-in feature.
2. Ensure that the message has a link for the user to click. Doing this confirms their subscription.
3. Remove and avoid any users who don’t complete the double opt-in process.

Verify your email list

A high bounce rate that exceeds 2% is a spam indicator. A consistently high bounce rate signals ISPs that you’re not checking the data you’ve acquired. An actual spammer will fire off thousands of emails with zero regard for who they’re emailing or if they have consent.

If your campaign has a high bounce rate, do this:

1. Export your email list from your ESP or CRM.
2. Upload the file to an email verifier. The tool will prune out fake, invalid, and outdated email addresses that cause hard bounces.

3. Download your results, and replace your old list with the new, clean one.

Try a real-time validator

To further your data hygiene efforts and avoid bounces, use an email validation API on your data collection forms. This tool will allow your form to call the verifier using the API and reject any invalid or problematic email entries.

Here’s how:

1. Consult your email verification provider. If they offer an API, consult their documentation for their API code.
2. Create an API key for your form. Label each key according to its use (e.g., newsletter signup).
3. Add both components to the webpage where your form is hosted.

With the API installed, your form will automatically detect and reject any invalid entries. It’s also helpful for alerting users to typos.

Set up email blacklist monitoring

To mitigate potential inbox bans, use a tool that proactively monitors your email blacklist status. It saves you time and grants you peace of mind that you’ll be alerted right away rather than allowing a blacklist problem to linger.

Here’s how to set up a monitor:

1. Create an account with a blacklist monitor provider like ZeroBounce. We offer one free monitor that scans your domain or IP every 24 hours.
2. Enter the domain or IP address you want to monitor.
3. Ensure that the toggles are selected for each blacklist.

Note – The ZeroBounce Blacklist Monitor will send an automated notification if a change is detected for any of the available blacklist services. In other words, if your domain or IP is already on that blacklist, you will not receive a notification.

Delete unengaged subscribers

When building an email list, focus on quality over quantity. If users never open your emails, delete them, as poor engagement can impair email deliverability.

Inactive email addresses also pose additional risks: they may increase your bounce rate or be repurposed into spam traps, which will lower your sender score.

Use inbox testing tools

Inbox placement testers allow you to check the deliverability of your email campaign before you send it. The results will inform you whether your email went to the inbox, the spam folder, or went missing.

Here’s an example of how to use ZeroBounce’s Inbox Placement Tester:

1. Name your test and copy the provided test addresses.
2. Create a campaign using your actual email. In the “to” field, enter the test addresses. Then, send the campaign.
3. Check your results in your dashboard.

Within minutes, you’ll learn if providers like Gmail or Outlook identify problems that direct your email to the spam folder. This process can help you identify common errors that can impair your email domain or IP over time.

Never email a spam complainer

Anyone can report your email as spam at any time – including people who agreed to opt in. It’s not fair, but here’s what you can do in response.

1. If you receive a spam complaint, treat it as an unsubscribe request. Remove the user from your list.
2. Add the email address to a suppression list. This is an extra precaution senders should take to avoid accidentally sending emails to the wrong people.

Additionally, an email verifier like ZeroBounce can detect abusive emails. These emails belong to users with a notable history of issuing or misusing spam reports. Because the threshold for spam complaints is so low (0.1%), it’s best to avoid these people altogether.

Many legitimate senders end up on email blacklists. They may follow some email marketing best practices, but failing to abide by even just one rule can get them into trouble.

How can you avoid being one of these senders? Here’s what our SMTP Deliverability Specialist Radu Pasarica has to say:

Our email deliverability expert also shares other common mistakes that can get your IP or domain on an email blacklist:

• Using an email list that you purchased or rented.
• Sending emails with fake or misleading header information.
• Emails with malicious content, such as viruses or phishing attacks.
• Getting a high email bounce rate. The benchmark is 2%.
• Receiving too many spam complaints. Getting one complaint for every 1,000 emails you send is understandable. Anything higher than that lets inbox providers know that your emails are bothering people.
• Keeping spam traps in your email list. See how spam traps impair your inbox placement.

Email blacklisting scares many senders, and for good reason. When the emails you work so hard for go to spam (or not even there), your efforts are futile. You may be spending hours crafting compelling emails for your customers, only to see that…

• No matter how relevant your content is, you can’t get people to engage with it.
• All the steps you’re taking to boost your metrics don’t make a difference.
• Your email revenue keeps dropping and affecting your entire business.

This happens because people don’t see your emails anymore. Before you throw in the towel on email marketing, run an email blacklist check. Identifying potential IP or domain blockage may be stressful at first. But on the positive side, at least now you’re able to get your email off that blocklist.

If you think your email has been blacklisted, get in touch with us. Our team has extensive experience helping senders reach the inbox and is available 24/7.

Hit the chat button in the bottom-right corner – or send us a message, and someone will be there to help today.