Which protocol is primarily used for email transmission over the Internet?

Simple Mail Transfer Protocol (SMTP) is the standard protocol specifically designed for sending and relaying email messages across the Internet. It operates over TCP port 25 and is responsible for the transmission of emails from a client to a server or between servers. SMTP handles the email delivery process, ensuring that messages are sent, routed, and delivered to the appropriate destination.

In contrast, the other protocols serve different purposes. Hypertext Transfer Protocol (HTTP) is used for transferring web pages and other content on the web, not for email. File Transfer Protocol (FTP) is designed for transferring files over a network, providing functionalities such as uploading and downloading files, without dealing with email transmission. Post Office Protocol (POP) is primarily utilized for retrieving emails from a server to a client, rather than sending them.

Understanding these distinctions highlights the specific role of SMTP in the context of email transmission, solidifying its importance in the overall functioning of email communications on the Internet.