Data Loss Prevention (DLP) discovers, classifies, and controls sensitive data as it moves (across email, endpoints, cloud applications, and collaboration channels), preventing exfiltration, misdirected sends, and compliance violations. This market evaluates the same email-security cohort through the DLP lens: platform suites with native DLP engines (Proofpoint, Forcepoint, Mimecast, Microsoft), gateway vendors with outbound policy and encryption controls (Cisco, Barracuda, Fortinet, Trustifi), API-based vendors extending into sensitive-data visibility (Abnormal, Material Security, Sublime), and human-layer risk reduction (KnowBe4, Hoxhunt).