Cisco Cisco Email Security Appliance C160 Mode D'Emploi

You can segregate incoming and outgoing email traffic over separate listeners and 
on separate IP addresses. However, the System Setup Wizard on the appliance 
supports initial configuration of the following configurations:

2 separate listeners on 2 logical IP addresses configured on separate physical 
interfaces
— segregates incoming and outgoing traffic 

1 listener on 1 logical IP address configured on one physical interface
— combines both incoming and outgoing traffic

Configuration worksheets for both one and two listener configurations are 
included below (see 

configuration scenarios are represented by one of the following three figures.