In this chapter, you will learn the following:
• Reasons for multinetwork and multi-interface configurations
• Configuring and using virtual gateways on ESA
• Other advanced network topics, including TLS for secure email transmission
The previous chapters deal with simple Email Security Appliance (ESA) network configurations. In most of the examples, the ESA uses a single IP address and hostname for all communications: inbound mail from the Internet, outbound mail from internal mailstores, and for management and monitoring protocols.
There are cases where this configuration is not adequate or simply not desirable. The ESA provides support for many different network topologies to suit your environment.