When a 3rd-party cookie is rejected, a default is displayed for all mboxes. Is this statement true or false?

The statement is true. When a third-party cookie is rejected, Adobe Target cannot store or retrieve information about the user, which leads to a fallback mechanism being activated for all mboxes. This default display is utilized because the system is unable to deliver personalized content or experiences, which rely on data collected via cookies. As a result, the visitor will see a generic default experience across all mboxes since the targeting and personalization that typically rely on those cookies cannot be executed. This response reflects how Adobe Target manages situations where cookie policies restrict its ability to gather data, thereby ensuring that a baseline experience is available even when personalization can't occur.