»The Surveillance of Content Data of E-Mails. Constitutional and Criminal Proceeding Aspects of an Investigative Measure with Special Consideration of the Fundamental Right to Protection of the Integrity and Confidentiality of Information Technology Systems«: How is an e-mail protected during the various stages of its transmission by the German Constitution and what does this imply for the applicability of existing criminal procedural requirements? The author analyses these questions with a special view to the requirements of the fundamental right to protection of the integrity and confidentiality of information technology systems and shows significant shortcomings with regard to the existing legal basis in the law of criminal proceedings.