Non-ASCII characters in Subject lines

[Stephen J. Turnbull]

Eli Zaretskii writes:

 > Is it allowed by the RFCs to have non-ASCII characters in the Subject
 > line of an email message?

The wire format of a header must contain no octets outside of the
range 0-127 inclusive.  More recent versions of the standard (ie, RFC
5322) restrict this further, disallowing most ASCII control
characters.  (IIRC, only TAB, CR, and LF are allowed by RFC 5322.)

 > Rmail currently doesn't decode this part, but maybe it should.

That doesn't make sense; there's nothing decodable there, it's raw
text.  Do you mean that Rmail should try to display a character glyph
rather than an octal escape or the like?

Trying to display should be optional (at least in theory, some
terminals may use some of those characters as control characters).
But it should be available, I guess (Postel Principle).

Note that in my experience almost all such headers are sent by
spammers, and the rest by programming wannabes.  Are you sure you
care?