Which command is used by SMTP to transmit email over TLS?

Which command is used by SMTP to transmit email over TLS?

• A. ENCRYPT
• B. TLSMAIL
• C. STARTTLS
• D. SECURESMTP

Answer: (C)

The main idea is upgrading an existing SMTP connection to a TLS-protected channel. STARTTLS is the SMTP extension that lets the client request a TLS upgrade after the initial connection. When the server indicates it supports TLS, the client issues the STARTTLS command; if accepted, a TLS handshake runs and the session switches to encrypted communication. From there, SMTP commands and mail data are transmitted securely over TLS. This explicit upgrade is different from implicit TLS (SMTPS), where TLS starts immediately on a dedicated port. The other names listed aren’t SMTP commands used for TLS, so STARTTLS is the correct choice.

The main idea is upgrading an existing SMTP connection to a TLS-protected channel. STARTTLS is the SMTP extension that lets the client request a TLS upgrade after the initial connection. When the server indicates it supports TLS, the client issues the STARTTLS command; if accepted, a TLS handshake runs and the session switches to encrypted communication. From there, SMTP commands and mail data are transmitted securely over TLS. This explicit upgrade is different from implicit TLS (SMTPS), where TLS starts immediately on a dedicated port. The other names listed aren’t SMTP commands used for TLS, so STARTTLS is the correct choice.