This section describes a more complex example with a parent DNS domain—starlight.com—for the corporate headquarters of the Starlight company, and a child DNS domain—eng.starlight.com—for the engineering division of the company. Consider the following issues for this configuration.
Each domain needs to send internal and external e-mail independently of the other.
The two domains must be able to send e-mail to each other.
Only one of the domains (starlight.com) has a connection to the Internet but both need to send and receive e-mail with Internet sites. The networks of both domains are interconnected.
At first, this example looks quite complex but you can handle it with five configuration files. ...