Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

In Figure 3-3, one public listener (A) and one private listener (B) are configured on the appliance in this 
Enterprise Gateway configuration.

Figure 3-4 further illustrates the differences between the default settings of public and private listeners. 
A public listener is intended to receive email from the internet. The public listener receives connections 
from many hosts and directs messages to a limited number of recipients. Conversely, a private listener is 
intended to receive email from your internal network. The private listener receives connections from a 
limited (known) number of hosts and directs messages to many recipients.

C10/100 customers: By default, the System Setup Wizard walks you through configuring one public 
listener for both receiving mail from the Internet and for relaying email from your internal network. That 
is, one listener can perform both functions. 

Later in the chapter, these differences will be demonstrated in the Host Access Table and Recipient 
Access Table for each type of listener. 

IronPort Email Security appliance

Internet

Large Small 

ISPs

SMTP

SMTP

corporations 

corporations 

Firewall

Groupware server

(Exchange™, Domino™, 

Groupware client

Groupwise™)

POP/IMAP server

POP/IMAP client

A

B