What command should be used to see which ports are currently open on a Linux mail server?

The command that is most suitable for checking which ports are currently open on a Linux mail server is netstat. When executed, netstat provides detailed information about network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. Specifically, using the netstat command with appropriate flags allows you to see active connections and which ports are listening for incoming connections on the server.

While lsof could be used to list open files and include network connections, it is more specific to processes and may provide more granular information than is necessary just to check open ports. The commands ipconfig and traceroute serve different purposes; ipconfig is used to view and configure network interface parameters on Windows systems, while traceroute is utilized to determine the path packets take to reach a destination over a network. Thus, using netstat is the most effective way to ascertain open ports on a Linux mail server.