Outbound Throttle in Proofpoint is an administrative control used to manage excessive outbound sending behavior from internal accounts. In the course structure for Threat Protection Administrator, Outbound Throttle is taught alongside send mail thresholds, which indicates that the feature is threshold-driven and intended to help administrators monitor and respond to abnormal outbound activity. Among the options provided, the behavior that aligns with this operational purpose is the ability to send a warning email to the administrator once the configured threshold is reached, including details about the sending account. That fits how an administrator would use the feature in a real environment: detect possible abuse, compromised accounts, or bulk-mail anomalies, then alert the responsible admin for investigation or remediation. The other options do not match standard Proofpoint throttling behavior. The feature is not described as a user self-warning mechanism, it does not calculate load and bypass filtering, and it is not simply a delayed quarantine-and-redelivery scheduler. Because the publicly accessible course outline references configuring Outbound Throttle and send mail thresholds but does not expose the full internal lab text, this answer is aligned to the administrator-facing threshold-and-alert behavior taught in the course context. On that basis, the correct option is the administrator warning email after threshold breach.