Cisco Hybrid Email Security is a unique service offering that combines a cloud-based email security deployment with an appliance-based email security deployment (on premises) to provide maximum choice and control for your organization. The cloud-based infrastructure is typically used for inbound email cleansing, while the onpremises appliances provide granular control - protecting sensitive information with data loss prevention (DLP) and encryption technologies. Reference: https://www.cisco.com/c/dam/en/us/td/docs/security/ces/overview_guide /Cisco_Cloud_Hybrid_Email_Security_Overview_Guide.pdf