SpamAssassin Rule: RCVD_IN_XBL
Standard description: Received via a relay in Spamhaus XBL
Explanation
The mail was received from a server listed in the Spamhaus Exploits Block List DNSBL, which lists hijacked PCs infected by illegal 3rd party exploits.
The XBL wholly incorporates data from two highly-trusted DNSBL sources, with tweaks by Spamhaus to maximise the data efficiency and lower False Positives. The main components are:
the CBL (Composite Block List) from cbl.abuseat.org
the NJABL Open Proxy IPs list from www.njabl.org.
Further Info
The default scores for this rule can be found in the online list of tests.