What is a black list

Domain Name System Blacklists, also known as DNSBL's or DNS Blacklists, are spam blocking lists that allow a website administrator to block messages from specific systems that have a history of sending spam.

 As their name implies, the lists are based on the Internet's Domain Name System, which converts complicated, numerical IP address such as into domain names like example.net, making the lists much easier to read, use, and search.

If the maintainer of a DNS Blacklist has in the past received spam of any kind from a specific domain name, that server would be "blacklisted" and all messages sent from it would be either flagged or rejected from all sites that use that specific list.

Not all Blacklists are equal

With over 300 publicly available blacklists, it’s no wonder good senders keep close eyes on their IP and domain activity. Public blacklists are created by large, trustworthy companies, as well as small, independent networks. Since anyone can create a blacklist, they don’t all have the same impact on deliverability. Mailbox providers and filtering companies do not leverage inbox placement on every blacklist. They typically combine data from various public blacklists, as well as data from their own networks, to determine your credibility as a sender.

Email marketers often associate blocking with being blacklisted. It’s important to note that blacklist providers are not the ones blocking your mail—it’s the mailbox provider leveraging your blacklist status that blocks your mail.

 If a blacklist resulted in a block, focus on the potential causes for the listing. Blacklisting is most often caused by poor list quality and end-user complaints.

There are two types of blacklists: IP address-based and domain-based.

IP-Based: Real-time Black Lists (RBL) and Domain Name Server Black Lists (DNSBL) are lists of IP addresses whose spam status changes in real-time.

Mailbox providers check these blacklists to see if the sending server is managed by a sender who allows others to connect and send from their system (open-relays).

They also check for known spammers or mailbox providers that allow legitimate spammers to use their infrastructure.

Any good sender’s reaction to a blacklisting is to request removal immediately. Note that this can often harm more than help. If a sender continuously requests removal without making the necessary changes, they run the risk of having all further requests automatically rejected.

Blacklist Removal Process

Determine why you are listed

Each blacklist has their own listing criteria that may include technical listings, policy listings, and evidence-based listings.

Technical listings are those that occur mostly from mail server configuration issues such as missing or incorrect reverse DNS records, missing on incorrect banner greetings, and mail servers operating in IP address space that an ISP has specified that mail servers should not be operating in.

 Policy listings are those based on an operator that does not wish to receive email from certain countries, or ISPs, or has a history of not honouring unsubscribe requests.

 Evidence based listings are those where the operator has received direct (or indirect) evidence that an IP address has been involved in sending unsolicited emails.

You'll need to visit the blacklist's website and perform a lookup on the specific IP address. Most blacklists will provide general listing reasons but will not provide access to the email addresses the spam was sent to.

Resolve the underlying issue(s)

Once you have determined why an IP address has been listed you can begin your internal process of resolve the issue.

 This is a good time to confirm that your network, mail server, and computers are properly configured. Common resolutions include: fixing forward and reverse DNS records, STMP banners, scanning all machines on the network for viruses, patching operating systems, configuring routers more securely, and enforcing strong passwords.

Follow the blacklist removal process

After you have fixed the issues you'll need to go back to the blacklist's website and follow their specific removal process.

Self-Service Removal

Some blacklists have a self-service removal feature. These generally allow for near immediate removal from the blacklist. Be sure that you've resolved the issue before doing this. When an IP address gets listed again after removal the process can become more difficult.

Time Based Removal

Most blacklists do not offer self-service or manual removal. They have a process that runs that will automatically remove low-level listings within a week or two. If the IP address has been involved in sending spam multiple times or in high volumes this process may take longer.

Things to keep in mind when contacting a blacklist operator

Blacklists are legal in most countries.

There is no point in threatening legal action against blacklists. Courts have ruled numerous times that they are legal. The blacklist is not preventing you from sending mail. The operator of the receiving mail server has made a person choice to consult a third party before accepting email from them. When all else fails contact the receiver's mail administrator over the phone to attempt to resolve the deliverability issue.

Don't lie.

Don't tell the operator you've resolved the problem when you haven't. If you lie that you've resolved the issue and it happens again they will likely not talk to you anymore.

Keep it polite and professional.

When you are having difficulty in removing a listing let them know what you are trying to do to resolve the issue. The more professional you are with them the more they'll be willing to help you resolve the issue. They are trying to stop people from receiving spam, not trying to keep you from legitimate non-spam correspondence.

To run a check on all of the major blacklists click the link below, it is a good idea to save this link and run a quick check every couple of weeks to ensure you keep your domain and IP in tip top order


It is very important to remove any blacklisted subscribers from your email marketing lists because they will have a detrimental effect on your sender reputation

Our autoresponder automatically removes all blacklisted contacts from your campaigns to ensure your reputation is not affected, you can find more details here


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