> Next question: how is it that a Control-N gets into the subject of a
> message? Is the sending program really trying to do something else, or is
> the transport eating the Contol-O's but not the Control-N's?

I don't have idea.

In general, SHIFT-OUT is used on 7bit transport environment to invoke
a character set which is designated on G1 (i.e. a character set which
is used when Most-Significant-Bit is set on 8bit environment.
This description is a bit over simplified, more accurate descriptioin
can be found on ISO-2022 standard which describes a way to extend
character set).

The character set which is designated on G1 depends on the codeset
of the message. If the message includes "<ESC> ) <final-character>"
or "<ESC> - <final-character>", the final-character indicates the
character set designated on G1. But this escape sequence might be
omitted in certain codeset.

The absent SHIFT-IN might be normal or not. It depends on the
codeset of the message. MIME charset name on Content-Type header
might helps, but the charset name might be misconfigured.
--
soda