nts without changing the however a little further advanced than EDI in as much as E-mail was principle behind the service offering. ON-NET PROCESS PROCESS PROCESS Figure 38.2 Premises based processing Technical infrastructure 38/5 VANS will continue to play a key role in the transition from 2. ADMD administrative domain, a public service provider proprietary network protocols to OSI transport through their trans- 3. PRMD - private domain, a company's internal service lation facilities. By offering translation it releases the individual 4. ORName - the originator/recipient name, a specific form of company from the need to harmonise its network offerings and address required by X.400 change procedures to those of all its trading partners. 5. P1 the protocol between MTAs, equivalent to the envelope 6. the protocol between UAs for IPM, equivalent to the structure of a memo with header and body Technical infrastructure 7. DNs delivery notifications, confirmation of receipt X.400 is generally used to refer to a series of recommendations As well as some refinements and extensions to the 1984 standard which provide an international standard for structuring and trans- (e.g. P2 was enhanced and became P22), another key concept was mitting electronic mail messages. So far there have been two itera- introduced in 1988, that of the message store (MS). A MS allows a tions of the four year cycle, yielding the 1984 and 1988 version of MTA to store a message it cannot immediately deliver to a UA e.g. the standards. when the UA is implemented on a PC which is periodically turned Since the early days it has been recognised that the base standards were suitable for transmitting other types of messages other than Whilst in practice the MS is extremely useful its use is optional. IPM SO the 1990 standard for built on the earlier work to define For the sake of clarity in the following discussion the MS is con- a complete ISO stack for EDI. However, industry could not wait for veniently omitted. the 1990 standard so work was done in Ame