What criteria does Braze use to determine the Unreachable Channels (MCE)?

The correct answer focuses on the specific criterion that identifies users as part of the Unreachable Channels (MCE). This option highlights users who possess sufficient data that would typically allow for a Minimum Effective Contact (MEC) calculation, yet they remain unreachable due to various factors such as blocking or technical issues.

Identifying this group is essential for understanding engagement levels and communication efficacy, as it allows marketers to hone in on users who might not be receiving messages as intended, despite having the data that suggests they should. This insight helps in strategizing how to potentially re-engage these users or improve the delivery of communications.

The other choices do not accurately encapsulate the specific definition of unreachable users as intended in the context of MEC. For instance, users opting out of all communications may not be counted as unreachable in the same way since their opt-out status deliberately indicates a lack of interest. Likewise, users who only engage with email campaigns aren't considered unreachable; they do interact, but perhaps only through one channel. Lastly, users who have never engaged with any messages lack the necessary data points to even evaluate for MEC calculation, making them a different demographic than those who might be included in the unreachable category.