What Are the Blacklists and How Do They Work

According to Statista, malicious content takes up to 50% of website traffic. If you do active mailings and notice that delivery rates to the inbox began to decrease — your IP address could be blocked. So, let’s find ways of how to avoid it.

What Is a Blacklist?

A blacklist is several IPs that have been blocked due to malicious activity. The purpose of blocking is to reduce the percentage of sending unwanted emails to clients. There are two types of them:

• Based on the sender’s domain.
• Based on the IP of the sender.

If the website is included in the blacklists database, the mailings will not be delivered at all or will go through additional spam filters.

Blacklists use different identification algorithms. For example, if a newsletter collects a lot of complaints about spam, then the percentage of delivery of letters to incoming mails decreases to zero.

How Do They Work?

These services use special traps and complaint info to identify web addresses that send malicious content. These traps are local emails that are placed on different sites and forums to detect malware senders.

Malware traps can be divided into two categories:

• converted emails that have been not active for more than a year;
• classic traps are specially designed emails.

All blacklists have various ways of calculating spammers. Blacklist operators have a large network of traps. They leave special emails on popular sites and forums, track them and blacklist any IP number that illegally leaves traps and does mailings on them.

The operator can initiate adding a website to the blacklist if it receives an excessive flow of complaints for spamming. To avoid blocking, you need to ensure the sending of mailings to valid and active addresses collected independently.

How to Verify a Website for Blacklisting?

To verify the IP of the certain server, mailing services refer to authoritative blacklist services. They request info about if users complained about malware activity. You can verify the IP on the CleanTalk site.

How to Decrease the Possibility of Being Blacklisted?

• Subscribe new users via double opt-in. When subscribing double opt-in, the user sends an email with a link for additional confirmation.
• Periodically clean the base from invalid addresses. Subscribers may lose interest in your newsletters — it is normal. Those users who do not continue to open mailings should be deleted from the database, otherwise, they may affect delivery over time.
• Set separate IPs for different types of mailing. Do not send all mailings from one address, because if they are blacklisted, the delivery of all mailings will be damaged.
• Provide the ability to quickly cancel subscription from the letters.

To maintain a high reputation as a sender, we recommend regularly check blacklists and analyze mailing rates. Good luck!