Which protocol is primarily used to send emails?

The correct answer is SMTP, which stands for Simple Mail Transfer Protocol. SMTP is specifically designed for sending emails from a client to a server and between servers. It operates by providing a set of rules that define how email messages are transmitted over the Internet. When a user sends an email, it is sent via SMTP to the recipient's email server, which stores the email and allows the recipient to retrieve it.

While other protocols like POP3 (Post Office Protocol) and IMAP (Internet Message Access Protocol) are used for retrieving emails from a server, they are not involved in the actual sending process. FTP (File Transfer Protocol) is unrelated to email as it is used for transferring files between computers on a network. The distinction between these protocols is essential for understanding how email functions within the digital communication landscape, highlighting SMTP's key role in the sending process.