IP Blacklist Check and Removal: Ultimate Guide to Blacklists

IP Blacklist Check and Removal: Ultimate Guide to Blacklists

The word ‘Blacklist’ makes the email marketer’s hair curl. But you know what they say: his bark is worse than his bite. After reading this article, everything will fall into place. Not only will you understand how blacklists work, but also gain the knowledge of dealing with them and keeping your reputation high.

What is IP Blacklist?

A blacklist is a real-time database of IP addresses or domains that have been known to send spam or malicious content. Many Internet Service Providers consult the blacklist databases in order to filter emails sent to the users within their network.

The result of having the sending IP address or domain on a blacklist can vary from being a small nuisance to a complete block of your email campaigns.

In order to have better deliverability, email marketers should have an understanding of why an IP or domain can get on a blacklist, what to do if the IP is blacklisted, and how to avoid getting the IP or domain on a blacklist.

How Do Blacklists Work?

Internet organizations, such as Mail Abuse Prevention Systems, monitor all IP addresses and domains that actively send emails and create databases of IP addresses/domains that are known in some way to be used to send spam. ISPs can use these databases when filtering emails from a sender. This is an important step to protect mailbox users from spam.

When you send an email, your sending IP address, which is the IP address of the SMTP server you use, is logged. It allows the receiving mail servers to determine who is sending the email and check if that sender has been known to send good or bad emails, by referencing the blacklists’ databases.

Here is the process:

  1. You send an email from marketing@domain.com to John Smith.
  2. John’s mail server determines your sender’s IP address (for example, and resolves it into a domain name.
  3. John’s mail server checks both the domain and IP against a database of IP/domains in a blacklist.
  4. If the IP address or the domain is blacklisted, your email will most likely land in John’s spam/junk mail folder, without the message content being scanned.
  5. If the IP or domain is marked as a repetitive spam sender, the ISP’s spam filters will reject your message, meaning it won’t even reach John’s spam folder.

Fix Email Deliverability: A Beginner's Guide to Blacklists

Why is My IP Blacklisted?

Open relay servers, hosts on certain websites, email spamming software, etc. are often added to blacklists. Some blacklists add IP addresses and domains based on user reports of unsolicited emails, e.g. complaint rate.

Spam complaints happen for very different reasons:

  • a recipient didn’t subscribe to the list;
  • a recipient didn’t find the unsubscribe link;
  • a recipient forgot opting it to the list;
  • a recipient receives too many emails;
  • content is not relevant to the recipient’s expectations.

A small complaint rate (<0,01%) is acceptable. If the number of complaints is higher than the allowed threshold, mailbox providers may start filtering the emails to spam folders or blocking the emails entirely.

Poor email list hygiene can also lead to blacklisting issues. Sending messages to old or inactive email addresses that could have been turned into spam traps, or harvested email addresses that are potential spam traps is destructive to your sender reputation.

Spam traps fall into two categories:

  1. Recycled spam traps. These are email addresses that were valid email accounts but have not been engaged with any message for a long time. Email messages sent to these addresses are typically returned by the receiving server for a year or more before the recycled email accounts are reactivated as spam trap addresses.
  2. Pristine traps. These are email addresses that are set up by anti-spam organizations and ISPs with the only purpose to determine spammers. They have never been used to sign up to an email list. Pristine traps most commonly get on mailing lists when senders purchase, rent, or harvest addresses.

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How to Know If My IP is Blacklisted?

You can visit the sites of the most popular blacklists such as Spamhaus, SURBL, SORBS, Invaluement, and SpamCop and look for your IP or domain listing there.

To save time, you can run a spam report with GlockApps. The report will show your email placement with different ISP and blacklist listings. GlockApps scans each sending IP address against 50+ blacklists including Spamhaus, SURBL, SORBS, and Invaluement.

GlockApps also checks the domains used in links in the message content against domain blacklists.

For dedicated IP addresses, GlockApps provides the real-time IP blacklist monitoring tool where you can add your sender’s IP address and have it scanned against dozens of popular blacklists automatically at a regular basis.

You will see where your IP is listed and receive the direct links to the blacklists’ websites to find more information about your IP listing and the de-listing process.

Another good idea is to analyze your bounce emails. If your deliverability is impacted by the blacklisted IP or domain, you will most likely receive a bounce email notification. The bounce error description will tell that your email was rejected because of an IP or domain listed on a blacklist.

In most cases, the bounce message includes the name or URL of the blacklist. An example of this type of message is

“Message rejected due to IP [] listed on RBL [X]”

The GlockApps Bounce Monitor can help you determine whether or not your messages are rejected due to blacklist listings. It gives in-depth bounce email analytics by the bounce type, bounce reason, sender domain, sender email address, and provider that rejected the message.

You can easily understand how many blocked messages you received, what the block reason was and which provider blocked your messages because of blacklisting issues.

GlockApps Bounce Monitor
GlockApps Bounce Monitor

How Do I De-List My IP or Domain from a Blacklist?

You should start by seeing which blacklists your IP or domain is on. Different blacklists have a different impact on email deliverability. Being listed on big blacklists (Spamhaus, SORBS, SURBL) will most likely lead to a spam folder placement or an entire email block while listings on small local blacklists can have zero impact.

If you don’t receive bounce emails because your sending IP or domain is blacklisted and the GlockApps delivery report shows a high inbox rate, then blacklists are not likely to influence your sender reputation. In the opposite case, blacklisting issues should be addressed.

It is important to remember that you can de-list your IP only if you own that IP. If you send emails from a pool of shared IP addresses that belong to an email service provider, you can only report the blacklisting issues to your email service provider.

At DNSBL sites, you can enter your IP to check your IP status, and then follow the instructions on how to be removed. Some blacklists have a manual de-listing process, some will do it automatically after some time.

The key here is to be proactive. Identify and fix the issues that got you to a blacklist (check your email acquisition sources, remove inactive users, verify the message content) before you contact the blacklist’s owner. They like to see that you’re taking it seriously and trying to solve your delivery challenges in a timely fashion.

Keep in mind these things when applying for a delisting:

  1. If you are a repetitive abuser, you will find it difficult, if not impossible, to be de-listed.
  2. Don’t dispute or argue. Focus on the facts they provide you and apply the remedies.
  3. If you know the cause of a listing, fix it first and then apply for de-listing.

Here is a good post to read more: How to Remove IP Address from Blacklist

How Do I Not Get Blacklisted?

Even legitimate email senders can end up in a blacklist due to their email sending habits. However, by using best email marketing practices, you will greatly reduce your risk of being blacklisted.

Here are the simple rules to follow:

  1. Don’t purchase or scrape email addresses. Instead, build your email list organically to make sure you are not hitting spam traps.
  2. Don’t send to email lists rented from 3rd party organizations even if you have a similar offer. Those people didn’t subscribe to your emails and are likely to report your email as spam.
  3. Use a confirmed opt-in process. You may end up with a smaller list but you win in quality. The confirmed opt-in process protects you from bots, malicious subscriptions, invalid email addresses caused by human typos, and spam traps.
  4. Remove inactive email addresses regularly. If a recipient has not engaged with your emails for the last 90 days, exclude their email address from your mailing list to avoid sending to a recycled spam trap.
  5. Monitor user complaints. Subscribe to feedback loops where it’s possible to receive email notifications when someone reports your email as spam. Remove complaining users from your list in a timely manner.
  6. Add an unsubscribe link to a prominent place. Make sure that the unsubscribe process is working and the recipient will not receive any further emails from you.
  7. Send content that is relevant to the recipient. If you have different mail streams (how-to’s course, newsletters, promotions, product-related campaigns, etc.) and allow users to choose the mailing lists to subscribe, don’t send all emails to all recipients. Respect their choice.
  8. Don’t send too much or too less. Find the best frequency in order to not overload the recipients and to not let them forget you. The best thing is to send as many emails as you promised on the subscription form.

You should remember that blacklists are not made to make the life of email marketers a nightmare. They are made to protect email recipients and help them receive the messages they desire. If you are doing everything to send relevant emails to confirmed subscribers, it will reduce the risk of getting on blacklists to a minimum and will make the process of getting delisted much much easier.

What is Email Spam Test and Why You Should Run It Every Time?

Email spam test is a tool that pinpoints elements of your letter that filters of different providers might see as spam.

Spam filters are constantly evolving and learning. There is no measure that will guarantee you deliverability for a lifetime. This means you should always test your email spam score, IP address, and email placement before you send an email campaign.

Moreover, you should run a spam test when you observe an unusual drop in your email open rate. It may be caused by a high number of your emails going to the recipients’ junk folders or blocked messages. And GlockApps is a good place to start testing and optimising your email deliverability.

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Julia Gulevich is an email marketing expert and customer support professional at GlockSoft LLC with more than 15 years of experience. Author of numerous blog posts, publications, and articles about email marketing and deliverability.