The correct answer is B. Stops processing a message in the same module once a condition is met. A Proofpoint Protection Server security-target reference states that when the Stop Other Rules option is selected, the system stops processing a message once a condition is met for the same SMTP callback that triggers a rule in a given filtering agent module. That wording directly supports the idea that the stop applies within the same module and callback context, not across every module globally.

This distinction matters because Proofpoint message processing is modular. A rule in one module can stop further rule evaluation in that module without necessarily preventing other modules from doing the work they are designed to do. That is why the “across all modules” answer is too broad and incorrect. The option is not a synonym for quarantine, nor is it a silent discard action. It is a rule-processing control that ends additional rule evaluation once the specified condition has been satisfied in the relevant module context.

In the Threat Protection Administrator course, this concept is important for understanding rule precedence and troubleshooting why later rules did not fire. If a message met a condition attached to Stop Other Rules, subsequent rules in that same module would not continue processing. Therefore, the verified course-aligned answer is B.