Which protocol provides rules for handling messages, such as moving them to quarantine?

The correct answer is DMARC. This protocol is specifically designed to improve email authentication and enforce policies for email messages, particularly regarding how they should be handled if they fail authentication checks. DMARC enables domain owners to define actions that should be taken when an email message does not align with the policies set for that domain, such as being moved to a quarantine state or rejected outright. This is critical for preventing phishing and spoofing attacks, ensuring that only legitimate emails reach their intended recipients.

On the other hand, while protocols like SMTP (Simple Mail Transfer Protocol) are crucial for the transmission of email messages, they do not provide rules for their handling after delivery. HTTPS (Hypertext Transfer Protocol Secure) is focused on secure communication over a computer network, mostly for web traffic, and is not related to email message handling. SIP (Session Initiation Protocol) is used for initiating, maintaining, and terminating real-time sessions that involve voice, video, and messaging applications, but does not pertain to the rules of dealing with messages in the context of email. Thus, DMARC stands out as the appropriate choice for establishing handling rules, including the option to move messages to quarantine.