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 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:
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

Each of the ASAs interfaces need to be grouped into one or more bridge groups. Each of these groups acts as an independent transparent firewall. It is not possible for one bridge group to communicate with another bridge group without assistance from an external router.
As of 8.4(1) upto 8 bridge groups are supported with 2-4 interface in each group. Prior to this only one bridge group was supported and only 2 interfaces.
Up to 4 interfaces are permitted per bridge-group (inside, outside, DMZ1, DMZ2)

The Mail Policies menu is where almost all of the controls related to email filtering happens. All the security and content filtering policies are set here, so it's likely that, as an ESA administrator, the pages on this menu are where you are likely to spend most of your time.