CBL

Update 9/1/21: The CBL zone has been effectively shut down and migrated over to Spamhaus XBL. If you have come here from a CBL blacklisting please visit our Spamhaus page (listed below) for instructions:

Spamhaus ZEN - BLACKLIST (mxtoolbox.com) (https://mxtoolbox.com/problem/blacklist/spamhaus-zen)

What is the CBL Blacklist?

CBL or Composite Blocking List is a DNS-based blackhole list of suspected e-mail services sending SPAM email resulting from virus or malware infections.

The CBL only lists IP Addresses exhibiting characteristics of:

• Various sorts of open proxies. An open proxy is generally a web server that allows email sending to piggyback on a script that sends email.
• Dedicated Spam BOTs used to send spam.
• Worms/viruses that do their own direct mail transmission.
• Trojan-horse or "stealth" spamware.

The CBLs gets its data from large mail server (SMTP) installations, most of which are large spamtraps.

How did I get on this Blacklist?

If you are on the CBL, it’s most likely you contracted a virus or BOTNET, typically via a malware-infected webpage. This is often a result of visiting a webpage that houses an infection which downloads malware on a PC. This malware (or virus) then creates a "mini SMTP" server used to hijack account information and send bulk email to recipients in the Users' email address book. It can affect the actual machine housing the "Email server platform" or on a local PC which is allowed to connect to the Email Server IP Address on SMTP port 25.

What the CBL Blacklist does not do

The CBL does not list open relays. It’s important to know the difference between and open relay and an open proxy, which the CBL DOES detect. An SMTP open relay is a real email server that has been misconfigured to accept email from a third party and send it out over the internet. An open proxy, on the other hand, is a non-mail server that’s been tricked into sending third-party email.

The CBL does not list URLs or URIs. Rather, it lists large quantities of IP addresses. It also does not make connections to other machines to test if one is infected. In other words, the CBL does not do probes.

The CBL also does not associate IPs with people or associations because most people on this list are victims of a virus rather than spammers. The CBL also does not accept external submissions. This makes it impossible for people to use the CBL as an instrument for revenge.

More Information about CBL

The CBL requires a manual de-listing request. The process, however, is fairly simple and straightforward.

IMPORTANT: The CBL expects you to resolve the underlying problem with your IP Address BEFORE you request delisting. If you do not resolve the underlying issue, then you will be relisted in their database if they continue receiving spam. If you continually request delisting without further researching the cause, you do run the risk of potentially being permanently blacklisted.