A security team has been alerted to a flood of incoming emails that have various subject lines and are addressed to multiple email inboxes. Each email contains a URL shortener link that is redirecting to a dead domain. Which of the following is the best step for the security team to take?


A. Create a blocklist for all subject lines.
B. Send the dead domain to a DNS sinkhole.
C. Quarantine all emails received and notify all employees.
D. Block the URL shortener domain in the web proxy.