Which is a feature of E-mail Security?

Layer-4 Monitoring is a network-level traffic inspection technique used in firewalls and IDS systems, not a feature of email security platforms.

Umbrella is Cisco's DNS-layer security product that blocks threats at domain resolution, and is not part of the email security feature set.

Outbreak Filters is a built-in feature of Cisco Email Security Appliance (ESA) that uses real-time threat data from Cisco Talos to quarantine malicious messages during the window between a new outbreak and the release of antivirus signatures. It applies dynamic rules based on message characteristics to stop threats proactively, making it a defining capability of the email security platform.

Investigate is a Cisco Talos threat intelligence and indicator-of-compromise analysis tool, not a feature of email security.