- About the volumes
- Download PDF of V5
- V1 - Introduction and Management
- V2 - Near Term
- V3 - Mid to Far term
- V4 - Interoperability Profile Guidance
- V5 - NISP Design Rules
- V6 - NISP - Annexes
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A.6. Messaging
155. The X.400 functional model and a typical client/server messaging configuration are shown in Figure A.1.
156. Whilst many mail server products support X.400, this is generally only for server-to-server connections (i.e. the products support the X.400 P1 protocol but not the P3 or P7 protocols). Moreover, whilst X.400-compliant UA and MS components are commercially available, they offer very limited functionality compared with mainstream COTS messaging products. These often include Groupware functionality as well as messaging functionality that would force many systems adopting X.400-compliant MS and UA products to provide more mainstream products.
157. For interoperability between domains, conformance with the P1 protocol standard (plus body part formats) is necessary but conformance with other protocol standards (i.e. P3, P7) is not.[5]
Figure A.1. X.400 Functional Model
[5] It is assumed that domain boundaries are organised such that direct access by a mail client in one domain to a server in another domain is not required; this will usually be precluded on security grounds in any event.