Which protocol is specifically designed for sending emails?

The protocol specifically designed for sending emails is Simple Mail Transfer Protocol (SMTP). SMTP is a foundational protocol in the email transmission process, allowing the sending of emails from a client to a server or between servers. It operates over a TCP connection and uses commands and responses to facilitate the transfer of message data.

Unlike other protocols listed, SMTP is focused solely on the sending aspect of email. While protocols such as Post Office Protocol 3 (POP3) and Internet Message Access Protocol (IMAP) are used for retrieving and managing emails from a server, they do not handle the sending of emails. HTTP, on the other hand, is a protocol used primarily for transferring hypertext via the web, not for email communication. Therefore, SMTP is the correct choice as it directly addresses the function of sending emails.