What feature does SMTP include to enhance security when sending emails?

SMTP, or Simple Mail Transfer Protocol, includes authentication mechanisms to enhance security when sending emails. These authentication methods, such as SMTP-AUTH, help verify the identity of the sender before allowing them to send emails through the server. This prevents unauthorized users from sending messages and reduces the risk of email spoofing and phishing attacks. By requiring proper authentication credentials, SMTP ensures that only legitimate users can access email services, thereby enhancing the overall security of email communications.

The other features listed, such as automated reply systems, mail filtering options, and message prioritization, play various roles in email functionality and management but do not specifically address security concerns associated with the sending process. Automated replies help manage incoming emails, mail filtering options help manage spam and unwanted messages, and message prioritization assists with organizing and directing email delivery based on urgency or importance. However, none of these features provide the secure identification and verification essential for protecting email transmissions in the same way that authentication mechanisms do.