Terminology - DMZ

Question

The term DMZ is used to describe a separation area between a trusted zone and an untrusted zone. Ex: internal network vs internet.
Can it be used to refer to a separation area between a trusted zone and a less trusted zone.?
For instance,in mail architectures, we often have a mail gateway in a DMZ and an internal mail server in an isolated network that connects for instance to a domain controller.
Can the isolated network that hosts the internal mail server be called a DMZ?

Answer 1

DMZ has its own detailed meaning which is fully described on Wikipedia. It implies a machine that receives all external traffic that is not already linked to an internal request to the predetermined DMZ controller.

Many people simply use DMZ as a means of bypassing the main router's firewall but it can be used to implement a more advanced firewall.

To answer your highlighted question directly, DMZ can indeed be applied at any and multiple levels of networking. So yes there could be a DMZ in the internal network between a trusted zone and a less trusted zone but that is not typically needed in most networks, as the router is usually sufficient to handle this.