Blacklist is a list of IP addresses that have been blocked by an email provider or spam filter for phishing and spam

If your IP address is on the blacklist, then the mailing will not be sent or will have to go through additional spam filters. According to Forrester Research, spam messages make up 67% of all email traffic. That is why ISPs should protect their clients from these types of messages. This can be achieved by filtering messages and checking the legality of the mail delivery. Using blacklists, the ISPs can reduce the number of spam messages in their networks. 

Email providers use blacklists that created based on publicly available information and internal ISP data. The blacklists use different spam identification algorithms, for example, "unwanted email." If you send "unwanted email" and it collects a lot of spam complaints, then there is a high probability that you will get onto the blacklist. 

ISPs use the most reputable blacklists – Spamhouse, Spamcop, and SORBS – to check the sending server IP addresses by requesting problem senders.

If your mailing has a high percentage of subscribers who mark your letter as spam, then the SendPulse server will get onto the blacklist. That is why, when using our server, you should follow the rules of our Antispam Policy.

To increase your email deliverability rate, SendPulse offers Email Verifier. With this tool, you can check your email addresses before sending a campaign. After the verification, you'll receive a list of valid addresses. This will help you stay out of the spam folder and keep your sender reputation high.


  1. This article develops a holistic view of email blacklisting. There's a definition, a list of companies that maintain blacklists, reasons why one may get on them, tips on how to avoid getting blacklisted.
  2. Here is a guide on how to reduce the risk of getting blacklisted.
  3. This article on our blog covers all aspects of blacklisting, including the way it works, how to check your IP address, and methods to get removed from it.
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