Electronic mailing systems are the dominant communication systems in private and business matters. Public administrations deliver documents to citizens and businesses—subpoenas, legal verdicts, notifications, administrative penalties, and so forth. However, official activities are more strongly bound to legal regulations than in civil law. Delivery of crucial and personal documents raises the demand for qualified identification and non-repudiation services as featured by registered and certified mail in the paper world. Legal requirements for electronic delivery carried out by public administrations (eDelivery) cannot be fulfilled by standard mailing systems. Although the requirements for eDelivery systems may differ due to national legal regulations, this paper discusses common requirements and properties on an abstract level. Moreover, the author shows how these requirements have been addressed by introducing the Austrian eDelivery system for eGovernment applications.