NEW VERSION:
NOTE: In certain transport domains, RFC 822 restrictions such as the
one that limits body-parts to printable ASCII characters may not be in
force. (That is, the transport domains may resemble standard Internet
mail transport, but without certain restrictions.) The relaxation of
these restrictions should be construed as locally extending the
definition of body-part, for example to include octets outside of the
ASCII range, as long as these extensions are supported by the transport
and adequately documented in the Content-Transfer-Encoding header field.
Please make it clear that in no event are headers (either message headers or
body part headers) allowed to contain anything other than ASCII characters.
(It may already be clear from the surrounding context, in which case no
change to the above text is needed.)
My biggest concern about standardizing 8-bit message formats is that people
will start to use non-ASCII characters in headers, and even in addresses,
and that our ability to exchange mail with one another will suffer as a
result.
Keith