Spreadsheets containing credit card numbers are being allowed to bypass the Cisco ESA.

Data Loss Prevention (DLP) is an outgoing mail policy feature that should be configured to catch this content before it leaves the network. DLP allows Cisco ESA to scan outgoing messages for sensitive or confidential data, such as credit card numbers, social security numbers, health records, etc., and apply appropriate actions, such as encrypt, quarantine, notify, etc., to prevent data leakage or loss.

The other options are not valid outgoing mail policy features to catch this content before it leaves the network, because they do not scan for sensitive or confidential data in messages.