Keith Moore wrote:
Actually, no. There was a difference in intent between the two. 1123 was
imposing new requirements on existing protocols, 1341 and 1342 were not
doing so. MIME implementation was not mandatory (as a matter of standards
compliance) for existing user agents.
Yes, in theory 1123 is mandatory and MIME compliance is not. In theory,
SMTP MTAs had to be compliant with RFC 821 as reaffirmed by 1123. In
practice most are not. The Internet SS isn't rounding up MTA authors
and throwing them in concentration camps. Certainly a UA can be
constructed which is not MIME-compliant (and indeed there are many of
those). However, while there is no standards requirement for MIME
support (and no enforcement even if there were a requirement), those
UAs which do provide MIME support are used in vastly greater numbers
than those that do not. Market forces are infinitely greater than
standards enforcement as far as the Internet is concerned.
None of which detracts from the facts:
1. It has been possible to generate internationalized phrases, comments
and unstructured field contents in any application of 822 text
message format since RFC 1342 (whether or not a particular
receiving UA is MIME compliant and properly displays the
encoded-words is another matter).
2. MIME (RFC 2047/2231) methods are the only means of handling non-ASCII
content in message header and MIME-part header fields in text
messages which is compliant with RFC 822 (and by extension to
applications, such as news, which use the 822 text message format).