Which protocol would you use for sending an email from one server to another?

The Simple Mail Transfer Protocol (SMTP) is the correct choice for sending emails from one server to another. SMTP is designed specifically for transferring email messages between servers. When an email is sent, it is transferred from the sender's server to the recipient's server via SMTP, making it an essential protocol for email delivery.

In contrast, other protocols serve different purposes:

Post Office Protocol 3 (POP3) is used to retrieve emails from a mail server to a local client, primarily in a way that downloads the emails and typically deletes them from the server. This means it does not facilitate the sending of emails.

File Transfer Protocol Secure (FTPS) is a protocol for secure file transfer over the internet and is not designed for email transmission at all.

Internet Message Access Protocol (IMAP) is another email retrieval protocol that allows users to access their emails directly from the mail server, maintaining the messages on the server rather than downloading them. Like POP3, it is not intended for sending emails.

Thus, SMTP stands out as the protocol specifically tailored for the sending aspect of email communication between servers.