An administrator needs to configure a server to restrict mail traffic to an application server for security reasons. Which of the following techniques can be used to manage this?

Port Address Translation (PAT) is a form of Network Address Translation (NAT) used to map multiple private IP addresses to a single public IP address using different port numbers, not for traffic restriction.

Access Control Lists (ACLs) are sets of rules applied to network devices like routers or firewalls that define which traffic is permitted or denied based on criteria such as source/destination IP address, port numbers, and protocols. By configuring an ACL, an administrator can explicitly block or allow mail traffic (e.g., SMTP on port 25 or SMTPS on ports 465/587) to or from the application server, providing granular security control.

Subnet masking is used to divide an IP network into smaller subnetworks and determine network/host portions of an IP address, not for restricting specific application traffic.

Port blocking is a general concept of preventing traffic on certain ports, but ACLs are the specific technique or mechanism used to implement this controlled restriction.