Well this is definitely an 822 msg so I've changed the list.
After writing my previous messages, I realized that TEXT-HEX would not
work very well for Japanese. The Japanese use a form of ISO 2022 that
uses only 7 bits, but each Japanese character uses 2 of the 94
printable ASCII characters, so changing & to && or &26 would actually
change 2 or more characters to something else (garbage). In many
cases, the user would be able to see that something happened to the
message, but sometimes the change would be subtle. In any case, this
is not very good for the Japanese users.
If you use 7 bits you are probably RFC821-clean already. So I'm not sure
why you'd need an escape. If you do then define a specific pair of
characters to be the escape instead of a single character.
The key point is that each Content-type should have its own set of
Content-encodings. So you don't have to use a single character for an
escape character in an encoding if that won't work well.
All I ask is that you put
Content-type: Japanese
Content-encoding: ISO2022-x
in the header of the message so that my mail UA knows how to display the
message (even if I can't then read it!).
If it is rejected, we send the 8-bit data using DATA
Definitely not acceptable -- but I'm not sure why you want to send 8 bit
data anyway.
Bob Smart