A brief review of RFC822 and RFC2045 leaves me slightly uncertain whether
or not a MIME content-type field follows the whitespace insertion rules for
an RFC822 structured header field.
A comment buried in section 5.1 of RFC 2045 (saying that comments may be
inserted in accordance with RFC822 rules for structured header fields)
suggests that this is the intent:
Note that the value of a quoted string parameter does not include the
quotes. That is, the quotation marks in a quoted-string are not a
part of the value of the parameter, but are merely used to delimit
that parameter value. In addition, comments are allowed in
accordance with RFC 822 rules for structured header fields. Thus the
following two forms
Content-type: text/plain; charset=us-ascii (Plain text)
Content-type: text/plain; charset="us-ascii"
are completely equivalent.
But I cannot find a cleat unequivocal statement either way.
The specific issue as stake here is whether the following is acceptable:
Content-type: image/tiff; boundary=