In a corporate environment, a company is designing its DMZ (Demilitarized Zone) to host a web server, an email server, and a DNS server. The security team is tasked with ensuring that the DMZ is properly segmented from the internal network while allowing necessary traffic to flow. Given the following requirements: the web server must be accessible from the internet, the email server should only accept traffic from the web server, and the DNS server must resolve queries from both the internal network and the internet. Which design principle should the security team prioritize to ensure both functionality and security in this DMZ setup?