IP and domain blacklists
This article covers IP email blacklists, and how they can affect the effectiveness of your email campaigns. This includes identifying the most common blacklists, the steps required to delist your IP from them, and more.
IP email blacklists, also known as DNS-based Blackhole Lists (DNSBLs) or Real-time Blackhole Lists (RBLs), are databases of IP addresses that have been reported or identified as sources of spam or other malicious activities. These lists are used by email servers and spam filters to block or filter out emails from known spammers.
Public blacklists
There are many popular IP email blacklists, such as Spamhaus or SORBS (Spam and Open Relay Blocking System), and most of them operate independently of one another. If an IP or domain are listed in public blacklists, you can look it up through public services like mxtoolbox.com
It's important to note that the impact of being listed on a particular blacklist can vary, and many mail servers use a combination of multiple blacklists for spam filtering. If you address issues that led to blacklisting on one service, this may also positively impact email delivery across other platforms. Additionally, understanding the specific filtering policies of the email service providers and implementing best practices for email security can help prevent future listings on popular blacklists.
Non-public blacklists
Many email security companies and services operate their own spam filters, blacklists, and internal threat intelligence models, without necessarily maintaining public, DNS-based Blackhole Lists (DNSBLs). These internal mechanisms are designed to detect and block email threats, spam, or malicious activity. The only way is to know that a specific IP or domain are listed on such a blacklist is to check our Creatio Bounce Monitor's server logs for rejection messages. Examples of companies that do this are Symantec, McAfee Email Protection, Cloudfare, and more.
Tools for checking an IP or Domain in blacklists
- MxToolbox
- DNSBL
These tools are each a list of the most popular blacklists. They serve as a scanner across all publicly available databases. To use, input the IP or domain and wait for results.
Delisting of the IPs
To delist your IP address from a blacklist, follow these general steps:
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Identify the Blacklist. Determine which blacklist(s) your IP address is listed on. You can use online tools like MxToolbox or check our Bounce Monitor server logs for rejection messages. Several of the blacklists mentioned above are always good places to start the search in.
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Investigate the cause. Identify and resolve the issues that led to your IP address being blacklisted. This may involve stopping spam or securing your mail server against abuse.
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Contact the Blacklist Operator. Visit the website of the blacklist operator and follow their delisting procedures. This often involves filling out a delisting request form and providing information about the steps you've taken to address the issue.
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Monitor Progress. Some blacklist operators provide tools to check the status of your delisting request. Monitor the progress and follow up if necessary.
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Prevent Future Listings. Take steps to prevent your IP address from being relisted. This may involve implementing strong security measures, using authentication mechanisms like SPF and DKIM, and monitoring your email traffic for signs of abuse.
It's important to note that the delisting process can vary between different blacklist operators. Make sure to carefully follow the instructions provided by each blacklist to improve your chances of successful delisting. Additionally, maintaining good email practices and securing your server against abuse is crucial for preventing future listings on these blacklists.