Which port should an administrator verify is enabled if clients cannot access a secure web server?

When clients are unable to access a secure web server, the relevant port to verify is 443. This port is used for HTTPS traffic, which is essential for secure communication over the web. Secure web servers utilize this port to establish encrypted connections, ensuring that data transmitted between clients and the server remains private and secure.

In an environment where secure web access is necessary, problems accessing a web server often stem from the blocking or misconfiguration of port 443. Thus, confirming that this port is enabled and properly routed is critical for clients to connect successfully to the secure web server.

The other options correspond to different network protocols: port 23 is used for Telnet, which is not secure; port 389 is for LDAP, primarily used for directory services; and port 445 is utilized for SMB, which is related to file sharing and printer services. None of these ports are applicable for secure web traffic, highlighting the significance of port 443 in this context.