The Spamhaus Policy Block List now covers One Billion IP addresses

This report provides a brief history and rationale for ISPs blocking or otherwise managing outbound SMTP on port 25 for residential and dynamic IP ranges, references a 2005 M3AAWG best-practices document, and explains how submitting dynamic ranges to the Spamhaus PBL helps reduce spam originating from infected end-user machines and lowers ISP abuse-handling overhead.