To send emails to loyalty members based on recent activity, a contact data entry source can be used to segment the data based on attributes and filters configured in Contact Builder. This allows for more flexibility and scalability than using a data extension entry source with an applied filter. Reference: https://help.salesforce.com/s/articleView?id=sf.mc_jb_entry_sources.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.mc_co_attribute_groups.htm&type=5