The E-Postbrief of Deutsche Post AG is a hybrid mail service (mix of electronic data transfer and classic mail delivery). The aim is to improve the security and privacy in electronic communication (as compared to non-encrypted e-mails). Prerequisite for the use of E-Postbrief is a registration. An encrypted website allows registered users to send electronic messages to other customers of the E-Postbrief service. If the recipient of an E-Postbrief has no electronic mail box (is not registered as an E-Postbrief customer), the message is printed, enveloped and delivered by mail carrier (hybrid E-Postbrief).