How to Delist from CBL

Blacklists are becoming active players in the email marketing field. A blacklist can be viewed as some kind of a guard that will allow certain emails to pass and stop others. From one side, blacklists do a good job by protecting email users from various kinds of spam and scam. On the other side, legitimate senders often suffer from the inability to deliver messages to their subscribers because of blacklists.

That’s why it is important for a sender to understand why an IP address can be blacklisted, how to delist the IP, and what to do to not get listed again. In this article, we’ll talk about the CBL blacklist.

What is CBL?

CBL is short for Composite Blocking List. The CBL creates its database of blocked IP addresses from different SMTP installations.

CBL does not attempt to list every IP address emitting spam. CBL lists the IP addresses which have the characteristics of open proxies of various sorts, spambots that have been abused to send spam, malware, and viruses, and some types of trojan-horse or “stealth” spamware. CBL also lists certain name servers primarily dedicated to the use of botnets.

With that said, the CBL blacklist lists an IP if:

there is an indication that the sending IP is infected with a spam-sending virus or worm;
the IP is primarily used in the operation of botnets;
the IP is acting as an open proxy for the sending of spam emails.

An “open proxy” is a non-email server turned into a machine sending email to third parties. These are often misconfigured or compromised web servers, web proxies or computers with spamware illicitly installed by a trojan downloader.

It doesn’t matter if an IP is dynamic or not. If the connections made from the IP indicate that it’s infected, it is listed regardless.

All the IP addresses appear on the CBL blacklist as a result of a virus or other compromise, not deliberate spamming.

CBL doesn’t provide any supporting data for listings explaining why a particular listing took place.

CBL does NOT list:

the IP addresses that are shared or are likely to be shared with legitimate senders;
the IP addresses of open SMTP relays.

An SMTP “open relay” is a misconfigured mail server that accepts any email from the Internet and allows it to be sent to anyone else on the Internet. Mail servers should be configured to reject incoming email that isn’t intended to a user in their base.

CBL doesn’t list the IP ranges (it lists only individual IP addresses) and does not list an IP address based upon the volume of emails sent from the IP.

How to Remove IP from CBL

Listings automatically expire after a period of time.

However, there is an easy removal procedure allowing any affected party to delist an IP address from CBL quickly.

You can start by doing an IP lookup on the CBL Lookup page.

If your IP address exists on the CBL’s blacklist, you will be given further instructions on how to delist it from CBL. Delisting if free.

Note that it is expected that you resolve the problem that led to the IP listing in CBL, preferably before you do a delisting because if a new indication of spam activity from the IP is subsequently detected, it will be listed again.

How to Avoid Being Blacklisted by CBL

Do a full security check of your email server to make sure you don’t have a virus, or an open proxy, or a trojan sending spam, or some sort of unusual misconfiguration which will cause your IP address to be listed or relisted on CBL.