What is the TCP port number used for POP3?

The Post Office Protocol version 3 (POP3) is primarily used for retrieving emails from a mail server, and it operates on TCP port number 110. This protocol allows clients (like email applications) to connect to their mail server and download emails to their local device, thereby enabling offline access and management of messages.

The other port numbers listed serve different purposes: the port 80 is associated with HTTP, which is used for transferring web pages, port 443 is for HTTPS, providing secure communication over a computer network, and port 25 is primarily used for SMTP (Simple Mail Transfer Protocol), which handles the sending of emails. Understanding the specific purpose of each port helps in effectively configuring and securing services on a network.