Which protocol utilizes TCP port 25?

SMTP, or Simple Mail Transfer Protocol, utilizes TCP port 25 for sending and relaying outgoing email messages between servers. This protocol is essential for email transmission on the internet, allowing servers to communicate and transfer messages effectively.

SMTP establishes a connection using TCP, which provides reliable, ordered, and error-checked delivery of data, making it suitable for the task of sending emails. When emails are sent from a client or server, they are initially directed to the mail server on port 25, which is the designated port for SMTP communication.

Other protocols mentioned in the options serve different purposes and use different ports. HTTP (Hypertext Transfer Protocol) typically uses port 80 for web traffic, FTP (File Transfer Protocol) commonly operates over ports 20 and 21 for file transfers, and POP3 (Post Office Protocol version 3) usually operates on port 110 for email retrieval. Understanding these ports and the functions of their respective protocols is important for network management and troubleshooting.