In Microsoft 365, Data Loss Prevention (DLP) policies are designed to “help you identify, monitor, and automatically protect sensitive information” across services such as Exchange Online, SharePoint Online, OneDrive, and Microsoft Teams. Microsoft’s guidance explains that DLP uses sensitive information types—including built-in classifiers like Credit Card Number—to detect when content matches a defined pattern and then enforce protective actions. With DLP, you can create rules that trigger when email messages contain customer lists with credit card numbers, and choose actions to block the message, restrict access, or notify and educate users via policy tips and incident reports. Microsoft further notes that DLP “prevents the accidental sharing of sensitive information,” can require user justification to override, and supports granular conditions (e.g., number of matches, recipients internal vs. external) to ensure that only risky transmissions are stopped. By applying a DLP policy to Exchange with the Credit Card Number sensitive info type, an organization can block or quarantine outbound mail that includes those numbers, thereby reducing regulatory and data-exposure risk. Other options listed—retention policies, conditional access, and information barriers—serve different purposes (data lifecycle, access/authentication conditions, and restricting communication between groups) and do not inspect message contents for sensitive data. Hence, DLP policies are the correct control to restrict sending emails that contain customer lists and associated credit card numbers.