|
|
|
@ -594,41 +594,41 @@ interoperability issues result from it:
|
|
|
|
|
of paragraphs that may be relevant in this context:
|
|
|
|
|
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
|
|
|
|
|
A body part is an entity and hence is NOT to be interpreted as
|
|
|
|
|
actually being an RFC 822 message. To begin with, NO header
|
|
|
|
|
fields are actually required in body parts. A body part that
|
|
|
|
|
starts with a blank line, therefore, is allowed and is a body
|
|
|
|
|
part for which all default values are to be assumed. In such a
|
|
|
|
|
case, the absence of a Content-Type header usually indicates
|
|
|
|
|
that the corresponding body has a content-type of "text/plain;
|
|
|
|
|
charset=US-ASCII".
|
|
|
|
|
|
|
|
|
|
The only header fields that have defined meaning for body parts
|
|
|
|
|
are those the names of which begin with "Content-". All other
|
|
|
|
|
header fields may be ignored in body parts. Although they
|
|
|
|
|
should generally be retained if at all possible, they may be
|
|
|
|
|
discarded by gateways if necessary. Such other fields are
|
|
|
|
|
permitted to appear in body parts but must not be depended on.
|
|
|
|
|
"X-" fields may be created for experimental or private purposes,
|
|
|
|
|
with the recognition that the information they contain may be
|
|
|
|
|
lost at some gateways.
|
|
|
|
|
|
|
|
|
|
NOTE: The distinction between an RFC 822 message and a body part
|
|
|
|
|
is subtle, but important. A gateway between Internet and X.400
|
|
|
|
|
mail, for example, must be able to tell the difference between a
|
|
|
|
|
body part that contains an image and a body part that contains
|
|
|
|
|
an encapsulated message, the body of which is a JPEG image. In
|
|
|
|
|
order to represent the latter, the body part must have
|
|
|
|
|
"Content-Type: message/rfc822", and its body (after the blank
|
|
|
|
|
line) must be the encapsulated message, with its own
|
|
|
|
|
"Content-Type: image/jpeg" header field. The use of similar
|
|
|
|
|
syntax facilitates the conversion of messages to body parts, and
|
|
|
|
|
vice versa, but the distinction between the two must be
|
|
|
|
|
understood by implementors. (For the special case in which
|
|
|
|
|
parts actually are messages, a "digest" subtype is also
|
|
|
|
|
defined.)
|
|
|
|
|
|
|
|
|
|
A body part is an entity and hence is NOT to be interpreted as
|
|
|
|
|
actually being an RFC 822 message. To begin with, NO header
|
|
|
|
|
fields are actually required in body parts. A body part that
|
|
|
|
|
starts with a blank line, therefore, is allowed and is a body
|
|
|
|
|
part for which all default values are to be assumed. In such a
|
|
|
|
|
case, the absence of a Content-Type header usually indicates
|
|
|
|
|
that the corresponding body has a content-type of "text/plain;
|
|
|
|
|
charset=US-ASCII".
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
The only header fields that have defined meaning for body parts
|
|
|
|
|
are those the names of which begin with "Content-". All other
|
|
|
|
|
header fields may be ignored in body parts. Although they
|
|
|
|
|
should generally be retained if at all possible, they may be
|
|
|
|
|
discarded by gateways if necessary. Such other fields are
|
|
|
|
|
permitted to appear in body parts but must not be depended on.
|
|
|
|
|
"X-" fields may be created for experimental or private
|
|
|
|
|
purposes, with the recognition that the information they
|
|
|
|
|
contain may be lost at some gateways.
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
NOTE: The distinction between an RFC 822 message and a body
|
|
|
|
|
part is subtle, but important. A gateway between Internet and
|
|
|
|
|
X.400 mail, for example, must be able to tell the difference
|
|
|
|
|
between a body part that contains an image and a body part
|
|
|
|
|
that contains an encapsulated message, the body of which is a
|
|
|
|
|
JPEG image. In order to represent the latter, the body part
|
|
|
|
|
must have "Content-Type: message/rfc822", and its body (after
|
|
|
|
|
the blank line) must be the encapsulated message, with its own
|
|
|
|
|
"Content-Type: image/jpeg" header field. The use of similar
|
|
|
|
|
syntax facilitates the conversion of messages to body parts,
|
|
|
|
|
and vice versa, but the distinction between the two must be
|
|
|
|
|
understood by implementors. (For the special case in which
|
|
|
|
|
parts actually are messages, a "digest" subtype is also
|
|
|
|
|
defined.)
|
|
|
|
|
{::include ../shared/fence-line.mkd}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|