$=q
Always quoted-printable encode Content-Type: V8.8 and later
The EightBitMode
(8) option
(EightBitMode on page 1025)
determines when and how 8-bit data will be encoded
into a 7-bit format. Ordinarily, the decision to use
quoted-printable as opposed to Base64 is made by
examining the input stream and choosing
quoted-printable if less than 1/8 of the first 4
kilobytes of data has the high bit set. Otherwise,
encoding is with Base64.
Beginning with V8.8, sendmail
offers the class $=q as the means to force the selection
of quoted-printable. Just before scanning the input
data, sendmail extracts the
type and
subtype from the
Content-Type:
header (Content-Type: on page
1154):
Content-Type: type/subtype; ...If the type is in the class
$=q, the body
will definitely be encoded with quoted-printable if
encoding occurs. Also, if a concatenation of
type, a slash (/), and
subtype is in class
$=q, the body
will definitely be encoded with
quoted-printable.
When sendmail first begins to
run, class $=q is
empty. A reasonable value in most countries might be
text/plain
(although probably not in countries that use 16-bit
characters, such as China). Other values for this
class might be text or text/html.
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