Email blocklist · DNSBL · IP addresses MON · 14 SEP 2026

CBL (Composite Blocking List)

Operated by Spamhaus / Abuseat · United Kingdom · Zone cbl.abuseat.org

About

Now part of the Spamhaus XBL list. Maintained as a standalone interface for legacy users; new deployments use Spamhaus ZEN directly.

Listing criteria

IPs observed sending spam, sourced from a wide range of honey-pots and feedback loops. Incorporated into the Spamhaus XBL since 2014.

How to query

For an IP address 1.2.3.4, query reversed-octets-dot-zone:

dig +short 4.3.2.1.cbl.abuseat.org

A returned IP (such as 127.0.0.2) means listed. Each blocklist has its own set of return codes meaning different things; the operator's documentation explains theirs.

Operator site Delisting / lookup › Return codes ›