This document specifies a standard XML interface that will enable software applications to call a secured electronic postal service (SePS), provided by a postal service, which is based on the concepts, schemas and operations described herein. The specification provides: - a definition of standard operations which can be combined to support secured electronic postal services; - a full description of all mandatory and optional request parameters required for use of these operations; - a full description of all response elements and the detailed circumstances under which they are returned. The specification also describes the functionality and edit rules of the actual technical specification artifacts, which are represented by an XML Schema (XSD) and an associated Web Services Definition Language (WSDL) specification. The versions of these applicable at the date of publication of this version of the specification are contained in this document as Annex A and Annex B respectively. These can also be obtained in electronic format from the UPU Technical Standards CD-ROM or from the UPU Standards Secretariat. In case of any conflict between Annex A and other provisions of this specification, Annex A shall be regarded as definitive. The SePS schema specification in Annex A is discreet and version specific. Postal Services are free to select which discrete interface versions they support. However, except in the case of upgrades to V1.15 adopted to ensure cross-border compatibility, postal services who upgrade from older versions of the schema (e.g. from V1.14) to a newer one are required to support backward compatibility of previously supported versions of the SePS interface specification as it applies to both processing requests/responses and honoring previously issued PostMarkedReceipts. Individual posts are free to address this backward compatibility challenge as they see fit. (....)