Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

 

 shows a very basic example of an incoming relay. Mail from IP address 7.8.9.1 appears to 

come from IP address 10.2.3.4 because the local MX/MTA is relaying mail to the Cisco appliance.

 shows two other, slightly more complicated examples of how mail may be relayed inside the 

network and how mail may be processed by several servers within the network before it is passed to the 
Cisco appliance. In example A, mail from 7.8.9.1 passes through the firewall and is processed by an MX 
and an MTA before being delivered to the Cisco appliance. In example B, mail from 7.8.9.1 is sent to a 
load balancer or other type of traffic shaping appliance and is sent to any one of a range of MXs prior to 
being delivered to the Cisco appliance.