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You may only send mailings with commercial content to existing customers with offers and advertisements about goods or services that are related to the products or services from previous purchase purchases of the customer. You must provide an easy opt-out option in each mailing, for instance an unsubscribe link in every e-mail which is sent out. Ensure receiptents can unsubscribe with one or two clicks, without signing in to an account or re-typing the email address. This will make sure that the chance that your e-mail will be reported as spam are much smaller.
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