The Cisco Email Security Appliance is an email security gateway product. Which is not an email-borne threat?

Spam is a widely recognized email-borne threat, typically involving unsolicited bulk messages, which Email Security Appliances are specifically designed to filter and block.

Phishing attempts are a major email-borne threat, involving fraudulent messages designed to trick recipients into revealing sensitive information, which email security solutions detect and prevent.

Malware, including viruses, ransomware, and other malicious software, is frequently distributed via email, making it a critical email-borne threat that security gateways defend against.

Junk E-mail is a subjective categorization for unwanted email, often synonymous with spam, but it is not a distinct technical threat type like phishing, malware, or spam that an Email Security Appliance is primarily designed to explicitly detect and mitigate. The appliance targets specific malicious behaviors and content.