Content-Transfer-Encoding:
Auxiliary MIME encoding RFC2045
The MIME Content-Transfer-Encoding:
header
describes what auxiliary encoding was applied to the
message body to allow it to pass through email
transport mechanisms that might have data or
character set limitations. Specifically, RFC821
requires message bodies to contain only 7-bit data.
To transport 8-bit data (such as images and sounds)
unless 8-bit is negotiated, it is necessary to
convert that data to 7 bits. The Content-Transfer-Encoding:
header
specifies precisely how that conversion was
done:
Content-Transfer-Encoding: how
Here how is defined by RFC2045 to
be one of the following: base64
(RFC2045), quoted-printable
(RFC2045, EightBitMode on page
1025), 8bit
(meaning that the message body contains unencoded
8-bit data in line length suitable for SMTP
transport), 7bit
(the message body contains 7-bit, SMTP-compliant
data), or binary
(the message body contains 8-bit data in a form that
is completely unsuitable for SMTP transport).
See the EightBitMode
option (EightBitMode on page 1025) for a
description of how V8 sendmail
converts between 8- and 7-bit data. The Content-Transfer-Encoding:
header
should never be declared in the configuration
file.
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