Duplicates in a German B2C list cause repeated contacts, inflate costs, and create compliance risk—a contact may unsubscribe from one record but continue receiving mail from another. Prevent duplicates at entry: use email address as the unique key and check new imports against existing records. For existing duplicates, merge carefully, preserving the most recent consent status, engage... https://www.b2cemaillist.com/germany-b2c-email-list/