A clean email list is a valuable asset. But it does not stay clean by itself. You must maintain it. Here is how. First, remove bounced emails immediately. They hurt your reputation. Second, update old contacts. People change jobs and email addresses. Third, remove duplicates. They waste your time. Fourth, respect opt-outs. If someone unsubscribes, remove them. Fifth, run regular audit... https://www.b2clead.org/8-2-million-targeted-germany-email-leads/