Which email protocol enables messages to be viewed without first downloading them from the email server?

The correct choice is the Internet Message Access Protocol version 4 (IMAP4) because it is specifically designed to allow users to access and manage their email directly from the server without needing to download the messages first. IMAP4 provides the capability to view, organize, and delete emails on the server in real-time, which enhances user flexibility and allows for better email management across multiple devices.

This protocol synchronizes the email client with the server, meaning that any changes made to the email (like marking it as read or moving it to a folder) are reflected across all devices that access the same email account. This is particularly advantageous for users who work on various devices, as they can maintain their email organization and status seamlessly.

In contrast, Post Office Protocol version 3 (POP3) works differently by downloading emails onto the user's device and, in many configurations, removing them from the server afterward. Simple Mail Transfer Protocol (SMTP) is utilized to send emails rather than retrieve them, and File Transfer Protocol (FTP) is used for transferring files, not specifically for email protocols. Each of these other options serves different purposes that do not support direct server access for viewing messages without downloading.