Which protocol is specifically designed for sending emails between servers?

The protocol specifically designed for sending emails between servers is SMTP, which stands for Simple Mail Transfer Protocol. SMTP works by facilitating the transfer of email messages from the sender's email server to the recipient's email server. When someone sends an email, it is routed through various servers, and SMTP governs this process, ensuring that the email is delivered correctly.

SMTP is essential in the email communication process primarily because it outlines how messages should be formatted, transmitted, and queued for delivery. It operates over a TCP connection, typically using port 25, which is specifically designated for this protocol.

IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol version 3) are both protocols related to the retrieval of emails from a server rather than sending them. IMAP allows users to access their emails from multiple devices while keeping the messages stored on the server, whereas POP3 downloads emails to the user's device and often removes them from the server.

FTP (File Transfer Protocol) is a protocol used for transferring files between computers over a network and is not related to email communication at all. Thus, the correct recognition of SMTP's unique role in sending emails clarifies its importance in the overall email infrastructure.