A system, method and software module for secure electronic communication services, wherein a public key (25) of private-public-key pair (30,25) is associated with an email address (24), internet name or other registered unique identifier; the registered user of the unique identifier holds the private-key (30) securely, and the respective public-key (25) is made accessible on a key server (6) for look-up and retrieval by other users, for encryption of communications to be sent to the holder of the private-key, and optionally for message confidentiality, message integrity and authentication of sender and recipient, without requiring certificates. A distributed and scalable system is provided by a server network (600; 401, 501) for registration, key distribution and management preferably using a kDNS server hierarchy (601,602,603) or a key-DNS server hierarchy (701,702,) and associated protocols so that public-keys of recipients can be searched and retrieved over the internet based on the recipients email address or other unique identifier, thus facilitating secure communication between users in different network domains and organizations.