Will@uunet.uu.NET (03/21/91)
Can someone tell me what are the key features present in X.400 addressing that are missing from SMTP-style addresses? As I understand it, X.400 is a superset of existing mail systems that tries to capture enough information in the mail address to make it unique on a global network. Specifically, what does it do in this respect that SMTP cannot do, and what are some of the other advantages of X.400? Can someone recommend a good article or book that compares the two transports in more detail? Thanks, Will Estes (apple!cup.portal.com!Will)
JPALME@qz.qz.se (Jacob Palme QZ) (03/25/91)
This is in reply to the question on what are the advantages with X.400 as compared to SMTP. In my opinion the main advantages with X.400 are: (1) There are standardized formats for delivery and non-delivery notifications. (2) Tracing och loop control is more fully standardized. (3) In addition to ordinary text, also other body part types are allowed, to send e.g. graphics and in the 1992 version of X.400 also any type of file, e.g. a binary file. (4) Standardized handling of distribution lists.
JPALME@qz.qz.se (Jacob Palme QZ) (03/26/91)
Answers to some questions I have received: (1) The advantage with standardized formats for delivery and non-delivery notifications is that the UA software can recognize these automatically, and handle them in the manner you want. The way this is to be done is not fully standardized, since X.400 is mainly a standard for the interchange of information between local systems, not a standard for how these local systems should work internally. (2) By tracing and loop control I mean that you add a log to a message of what has happended during its transmission (which domains it has passed etc) so that if by error the same message goes around and comes back to the same domain once more, it will be stopped and not looping around indefinitely. (3) Of course the RFC821/822 type of mail handling could be extended with all the features where X.400 at present has advantages. However, one should first discuss what is best, to convert to X.400 or to extend RFC821/822 with more features! The advantage with converting to X.400 is that we will at some time in the future avoid the problem of two different standards, with problems of gatewaying etc. Of course I understand that RFC821/822 style mail will continue to live for a long time even if it will gradually be phased out and replaced by X.400. At the very least, if RFC821/822 is to be extended with new features similar to those in X.400, this should be done in a manner which is highly compatible with how X.400 does the same thing. (4) More information about X.400 handling of distriubtion lists can be found in F.400(1988) or in MOTIS (ISO 10021) part 1. That part is an introduction to X.400/MOTIS, it contains a fairly good description of distribution list handling in X.400.