What does the POP3 protocol primarily handle?

The correct answer indicates that the POP3 protocol primarily handles retrieving email. The Post Office Protocol version 3 (POP3) is specifically designed for downloading email messages from a mail server to a local email client. When a user configures their email client to use POP3, the client connects to the mail server, retrieves the messages, and then typically removes them from the server, allowing offline access to emails.

The function of retrieving email is a crucial part of how email communication is structured, as it allows users to access their messages anytime and anywhere, even without an internet connection after the retrieval process.

Other functionalities mentioned in the question, such as sending, relaying, or encrypting email, are managed by different protocols or technologies. For example, sending email is typically handled by the Simple Mail Transfer Protocol (SMTP), while email encryption would be applied by standards like S/MIME or PGP. Therefore, focusing on its core purpose, POP3 is indeed primarily about retrieving email from a server.