The present document specifies the formats for messages that are produced and handled by a Registered Electronic Mail (REM) service according to the concepts and semantic defined in ETSI EN 319 522 parts 1 [7] and 2 [8] and ETSI EN 319 532 parts 1 [10] and 2 [11]. More specifically: a) Specifies how the general ERDS concepts like user content and metadata are identified and mapped in the standard email structure. b) Specifies how the aforementioned concepts are mapped in the REM service messaging structures. c) Specifies how the ERDS evidence set is plugged inside the REM service messaging structures. d) Specifies additional mechanisms like digital signature and other security controls.