SMTP, or Simple Mail Transfer Protocol, is a vital standard for email transmission. It’s responsible for sending, receiving, and relaying email messages. Understanding how SMTP works can provide insight into its essential role in digital communications.

An SMTP server is a computer program that sends, receives, and relays emails. It ensures that outgoing emails reach their destination. When you send an email, it’s first sent to an SMTP server. The server then processes the email and routes it to the recipient’s mail server, which stores it until retrieved.

Once connected, a series of commands (SMTP commands) are exchanged. These include HELO (or EHLO), MAIL FROM, RCPT TO, DATA, and QUIT. Each command has a specific function in the transmission process. HELO introduces the client to the server, MAIL FROM specifies the sender’s address, and RCPT TO identifies the recipient. DATA transfers the message body, and QUIT closes the connection.

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