How to find the users who were held back from a certain message/campaign?
When users are sent a message, we generate an event that looks in the dashboard as "<MESSAGE_NAME> Sent".
Similarly, if a user falls in the Control group of a holdback, we generate a "Held Back" event for this, that looks like "<MESSAGE_NAME> Held back". Use this event to find users who were part of the control group.
In case this event is not yet available in the drop-down menu, refer to this guide on how to check it:
For campaign holdbacks, you need to filter all top-level messages as explained in this guide: