DNSBL check

About the DNSBL check tool

Managing mail servers can be a struggle, causing massive headaches. DNS Blackhole Lists (DNSBL) (aka 'IP blacklists' or just plain and simple 'blacklists') are one of those factors that may lead to serious issues in basic email delivery.

The DNSBL check tool performs a real-time check of the top DNSBLs worldwide, providing you with up-to-date insights into your server's reputation and status.

For each checked DNSBL, you'll find website and delisting information as well.


What is a DNSBL, and how does it work?

A DNS Blackhole List (DNSBL) is a mechanism to identify and block email from known sources of spam. It operates by querying a DNS server that maintains a list of IP addresses associated with spamming activities.

How can I implement DNSBLs on my mail server?

Integrating DNSBLs into your mail server involves configuring the server to query designated DNSBL servers during the email filtering process. Each mail server software may have specific steps for implementation.

What are the potential drawbacks of using DNSBLs?

While effective, DNSBLs may occasionally block legitimate emails, leading to false positives. It's crucial to carefully select and monitor DNSBLs to minimize the risk of blocking genuine messages.

My mail server IP has been blacklisted. What should I do?

If your mail server is blacklisted, first identify the DNSBL responsible. Check the blacklist provider's website for delisting procedures, follow their guidelines, and address any underlying issues causing the blacklisting.

Why are my recipients not receiving my emails? Could it be a DNSBL issue?

DNSBLs can contribute to delivery issues. Investigate whether your server IP is listed on any DNSBLs and take necessary delisting actions. Additionally, check email server logs for clues on why emails may be getting flagged.

How do DNSBLs gather information about spam sources?

DNSBLs compile lists of spamming IP addresses through various means, including spam trap emails, user reports, and automated analysis of email traffic patterns. Understanding the data sources helps in evaluating the reliability of a DNSBL.

What actions can I take to prevent future blacklisting?

Regularly monitor your server for any signs of spamming activities. Implement best practices, such as SPF, DKIM, and DMARC, to enhance email authentication and reduce the risk of being blacklisted.


This tool has a fully-featured API available. You may read more about the API here. It is also an option to simply try out the tool - the corresponding API URL for each lookup is made available as a part of the result.


These tools are still in active development. If you have any kind of feedback, please let me know. Send me an e-mail on iamrootdottech(a)gmail.com.