Thomas Roessler <roessler(_at_)does-not-exist(_dot_)org> writes:
Note: If any line begins with the string "From", it is strongly
suggested that either the Quoted-Printable or Base64 MIME encoding
be applied. If Quoted-Printable is used, at least one of the
characters in the string should be encoded using the hexadecimal
coding rule. This is because many mail transfer and delivery
agents treat "From " (the word "from" followed immediately by a
space character) as the start of a new message and thus insert a
right angle-bracket (>) in front of any line beginning with "From"
to distinguish this case, invalidating the signature.
Perhaps you can add the following text?
If neither the Quoted-Printable nor Base64 MIME encoding is used,
and the charset provides alternative encodings of ASCII characters,
at least one characters in the string "From " shall be encoded in
such a way. Alternatively, if the charset provides (control)
characters without visible or semantic effect, such characters shall
be used to make the ASCII representation of the beginning of the
line distinct from "From ".
AFAIK, ISO-2022-JP provides such noop characters (and UTF-7 provides
an alternative encoding for ASCII characters, with UTF-8, you could
use the BOM---which is, unfortunately, not without semantic effect,
but that's a Unicode design problem anyway). This way, one of the
main problems which requires mandated Quoted-Printable encoding can be
addressed by ISO-2022-JP users, even if they use a 7bit CTE.
BTW: I've recently seen a line starting with "from " which was
mangled. Your text does not indicate if
--
Florian Weimer
Florian(_dot_)Weimer(_at_)RUS(_dot_)Uni-Stuttgart(_dot_)DE
University of Stuttgart http://cert.uni-stuttgart.de/
RUS-CERT +49-711-685-5973/fax +49-711-685-5898