What is the main purpose of the SMTP protocol?

The main purpose of the SMTP (Simple Mail Transfer Protocol) is to facilitate the sending and receiving of email messages across the internet. SMTP is specifically designed to handle the process of sending email from a mail client to a mail server or between servers. It operates primarily by establishing a connection to a mail transfer agent (MTA) and transferring messages using a set of commands defined in the protocol.

Unlike protocols that are used for retrieving emails, such as POP3 or IMAP, SMTP is focused solely on the sending aspect. Therefore, while it would connect to both the sending and receiving servers to manage the flow of messages, its core function is transmitting the actual email data.

The answers that revolve around retrieving emails, providing secure web connections, or converting formats do not align with SMTP's designated role in email communication. Those aspects are managed by other protocols and services, which highlights the specialized nature of SMTP as an effective and essential protocol for email delivery.