Announcing new users of an electronic communications system includes receiving an indication of a new user of an electronic communications system. The new user has an identifier for the electronic communications system. Existing users of the electronic communications system that are known to the new user are identified. The identified existing users are sent a message notifying the identified existing users of the identifier of the new user. The identified existing users may be enabled to add the identifier of the new user to participant lists used by the identified existing users. The new user may be enabled to add identifiers of the identified existing users to a participant list of the electronic communications system used by the new user.