Cisco Cisco Email Security Appliance X1070 User Guide

The Cisco Virtual Gateway technology allows you to configure enterprise mail gateways for all domains 
you host — with distinct IP addresses, hostname and domains — and create separate corporate email 
policy enforcement and anti-spam strategies for those domains, while hosted within the same physical 
appliance. 

The number of Virtual Gateway addresses available to you depends on the model of your appliance. 
Some appliance models can be upgraded to support more Virtual Gateway addressed via a feature key. 
Contact your Cisco sales representative for more information about upgrading the number of Virtual 
Gateway addresses on your appliance. 

Cisco has developed a unique Virtual Gateway technology designed to help ensure that corporations can 
reliably communicate with their customers via email. Virtual Gateway technology enables users to 
separate the appliance into multiple Virtual Gateway addresses from which to send and receive email. 
Each Virtual Gateway address is given a distinct IP address, hostname and domain, and email queue.

Assigning a distinct IP address and hostname to each Virtual Gateway address ensures that email 
delivered through the gateway will be properly identified by the recipient host and prevents critical email 
from being blocked as spam. The appliance has the intelligence to give the correct hostname in the 

SMTP 

HELO

 command for each of the Virtual Gateway addresses. This ensures that if a receiving Internet 

Service Provider (ISP) performs a reverse DNS look-up, the appliance will match the IP address of the 
email sent through that Virtual Gateway address. This feature is extremely valuable, because many ISPs 
use a reverse DNS lookup to detect unsolicited email. If the IP address in the reverse DNS look-up does 
not match the IP address of the sending host, the ISP may assume the sender is illegitimate and will 
frequently discard the email. The Cisco Virtual Gateway technology ensures that reverse DNS look-ups 
will always match the sending IP address, preventing messages from being blocked accidentally.

Messages in each Virtual Gateway address are also assigned to a separate message queue. If a certain 
recipient host is blocking email from one Virtual Gateway address, messages intended for that host will 
remain in the queue and eventually timeout. But messages intended for the same domain in a different 
Virtual Gateway queue that is not being blocked will be delivered normally. While these queues are 
treated separately for delivery purposes, the system administration, logging and reporting capability still 
provide a holistic view into all Virtual Gateway queues as if they were one.

Before setting up the Cisco Virtual Gateway addresses, you must allocate a set of IP addresses that will 
be used to send email from. (For more information, see the “Assigning Network and IP Addresses” 
appendix.) You should also ensure proper configuration of your DNS servers so that the IP address 
resolves to a valid hostname. Proper configuration of DNS servers ensures that if the recipient host 
performs a reverse DNS lookup, it will resolve to valid IP/hostname pairs.

After the IP addresses and hostnames have been established, the first step in configuring the Virtual 
Gateway addresses is to create new IP interfaces with the IP/hostname pairs using the Network > IP 
Interfaces page in the GUI or the 

interfaceconfig

 command in the CLI.