What action must be taken before using a group refresh activity?

Before using a group refresh activity, it is essential to create a group definition. This action serves as the foundational step, as a group definition establishes the criteria that will determine which subscribers are included in the group. The group refresh activity then uses this predefined set of specifications to update the group's membership based on the current data.

Creating a group definition involves identifying the relevant attributes or filters that will define the group's demographics or behaviors. Once the group definition is set, the refresh activity can effectively pull and update the data, ensuring that the group remains current and reflects any changes in subscriber information or status.

The other actions mentioned, such as importing subscriber data, defining email templates, or generating reports, while relevant to the broader context of email marketing, do not directly precede the use of a group refresh activity. They serve different purposes in the marketing automation workflow but do not establish the necessary criteria for the group itself.