I was disappointed to see HSJ perpetuating the myth that X.400 is an older standard than SMTP (e-novation, page 13, 15 March). In fact, X.400 is considerably newer and technically better than SMTP.
The first specification of SMTP was given in RFC-821 but this was based on the mail transfer protocol which itself is based on the ARPANET (the precursor of Internet) mail protocol defined in the early 1970s.
SMTP is, as the name implies, a simple text-based protocol, intended for transmitting unstructured text messages. It can only transmit ASCII text characters. In order to transmit binary files, some encoding mechanism had to be used, the most common of which was Uuencode.
On the other hand, the X.400 series of standards was developed as a set of formal international standards by CCITT (new ITU-TS) in 1984 and published in the 'Red Book'.
It was able to transmit any number of attachments (binary) and had many facilities additional to those in SMTP (for example, notification of delivery of a message).
The standards were revised in 1998 (mainly to add further security features) and again in 1993 (this is the current version). The standard was also adopted by the International Organisation for standardisation as the seven-part standard ISO 10021.
SMTP was then enhanced to include some of the facilities available in X.400 and an extension called 'MIME' was developed 'to allow multipart textual and nontextual message bodies to be represented and exchanged without loss of information'. Even using MIME, it is not possible to send binary files directly - they still have to be encoded (usually using 'Base-64' encoding which increases a message size by 33 per cent).
There were two serious problems with X.400 (which is why the older SMTP is now more generally used). The first is that the address formats were extremely cumbersome. The second is that users usually had to pay for the software, whereas SMTP implementations were 'bundled in' with many operating systems (and hence apparently free).
The SMTP/X.400 debate is similar to that for video-recorder formats (Betacom/VHS), where the better one technically failed due to commercial pressures.
Nevertheless, I hope that you do not continue to perpetuate the myth that SMTP is a newer or better standard than X.400.
Dr Adrian Stokes London NW7