You can't buy data hygiene

The report outlines how spammers historically performed 'dictionary attacks' against mail servers to validate email addresses and explains that early data-hygiene companies repurposed similar SMTP address verification techniques—sometimes adding checks to detect permissive servers—resulting in abusive traffic that ISPs block and forcing services to rotate IPs and domains. It is a descriptive, historical account of abusive email-harvesting practices rather than a report of a specific security incident.