Руководство Пользователя для Cisco Cisco Email Security Appliance C190

In the following example, the IronPort appliance (ironport.example.com) is a 
backup MTA for the domain example.com, since its MX record has a higher 
priority value (20). In other words, the higher the numeric value, the lower the 
priority of the MTA.

By registering the IronPort appliance in DNS, you will attract spam attacks 
regardless of how you set the MX record priority. However, virus attacks rarely 
target backup MTAs. Given this, if you want to evaluate an anti-virus engine to its 
fullest potential, configure the IronPort appliance to have an MX record priority 
of equal or higher value than the rest of your MTAs.

You may want to review all features of the appliance prior to installing. 

 provides an overview of all functions 

available on the appliance that may affect the placement of the IronPort appliance 
within your infrastructure.

Most customers’ network configurations are represented in the following 
scenarios. If your network configuration varies significantly and you would like 
assistance planning an installation, please contact IronPort Customer Support (see 

).

The following figure shows the typical placement of the IronPort appliance in an 
enterprise network environment: 

$ host -t mx example.com

example.com mail is handled (pri=10) by mail.example.com

example.com mail is handled (pri=20) by ironport.example.com