Collection, Processing and Use of Personal Data Basically, you may visit ISTENNIS without us collecting any personal data from you. Personal data is only collected if you voluntarily disclose such data for the purpose of concluding a contract or opening a customer account. Without your explicit consent, this data is merely used for contract performance and processing your inquiries. Upon complete fulfillment of the contract and complete payment of the purchase price your data will be stored with care for tax and commercial law retention periods, to be deleted upon expiry of these periods. Furthermore, personal data is collected, if you subscribe to our e-mail newsletter. We use this data for our own advertising purposes in terms of our e-mail newsletter provided you have explicitly consented to it. You may unsubscribe from our Newsletter at any time using the respective link in the Newsletter or by sending us a message. Your e-mail address will be deleted immediately after unsubscribing.