header field
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... A MIME-Version header field, which uses a version
number to declare a message to be conformant with MIME
...
... A Content-Type header field, generalized from RFC 1049hist,
which can be used to specify the media type ...
... A Content-Transfer-Encoding header field, which can be
used to specify both the encoding transformation that
...
... further describe the data in a body, the Content-ID and
Content-Description header fields. ...
...
All of the header fields defined in this document are subject to the
general syntactic rules for header fields ...
... header fields defined in this document are subject to the
general syntactic rules for header fields specified in RFC 822std11(-> 2822prop). In
particular, all of these header fields ...
... header fields specified in RFC 822std11(-> 2822prop). In
particular, all of these header fields except for Content-Disposition
can include RFC 822std11(-> 2822prop) ...
... The term "entity", refers specifically to the MIME-defined header
fields and contents of either a message or one of the parts in the
body of a multipart entity. The specification of such entities is
...
... MIME defines a number of new RFC 822std11(-> 2822prop) header fields that are used to
describe the content of a MIME entity ...
...
The formal definition of these header fields is as follows:
...
... fields version CRLF ; The ordering of the header fields implied by this BNF definition should be ignored. ...
... entity-headers [ fields ] ; Any field not beginning with "content-" can have no defined meaning and may be ignored. The ordering of the header fields implied by this BNF definition should be ignored. ...
... MIME-Version Header Field ...
...
Therefore, this document defines a new header field, "MIME-Version",
which is to be used to declare the version ...
...
Messages composed in accordance with this document MUST include such
a header field, with the following verbatim text:
...
...
The presence of this header field is an assertion that the message
has been composed in compliance with this document.
...
...
Note that the MIME-Version header field is required at the top level
of a message. It is not required for each body part of a multipart
...
... Content-Type Header Field ...
...
HISTORICAL NOTE: The Content-Type header field was first defined in
RFC 1049hist. RFC 1049hist ...
...
The Content-Type header field specifies the nature of the data in the
body of an entity by giving media type ...
... media type and subtype names, the remainder
of the header field is simply a set of parameters, specified in an
attribute=value notation. The ordering of parameters is not
significant.
...
... media
types. Truly global mechanisms are best addressed, in the MIME
model, by the definition of additional Content-* header fields.
...
... Syntax of the Content-Type Header Field ...
... Augmented BNF notation of RFC 822std11(-> 2822prop), a Content-Type header field
value is defined as follows:
...
... Note also that a subtype specification is MANDATORY -- it may not be
omitted from a Content-Type header field. As such, there are no
default subtypes.
...
... parameter value. In addition, comments are allowed in
accordance with RFC 822std11(-> 2822prop) rules for structured header fields. Thus the
following two forms
...
...
This default is assumed if no Content-Type header field is specified.
It is also recommend that this default be assumed when a
syntactically invalid Content-Type ...
... It is also recommend that this default be assumed when a
syntactically invalid Content-Type header field is encountered. In
the presence of a MIME-Version header field ...
... header field is encountered. In
the presence of a MIME-Version header field and the absence of any
Content-Type header field ...
... header field and the absence of any
Content-Type header field, a receiving User Agent can also assume
...
... MIME-Version or the
presence of an syntactically invalid Content-Type header field, but
the sender's intent might have been otherwise.
...
... encodings will be indicated by a new "Content-
Transfer-Encoding" header field. This field has not been defined by
any previous standard.
...
... Content-Transfer-Encoding: 7BIT" is assumed if the
Content-Transfer-Encoding header field is not present.
...
...
If a Content-Transfer-Encoding header field appears as part of a
message header, it applies to the entire body of that message. If a
...
... message header, it applies to the entire body of that message. If a
Content-Transfer-Encoding header field appears as part of an entity's
headers ...
... Content-ID Header Field ...
... one body to make reference to another. Accordingly, bodies may be
labelled using the "Content-ID" header field, which is syntactically
identical to the "Message-ID" header field ...
... Content-Description Header Field ...
... "image" body as "a picture of the Space Shuttle Endeavor." Such text
may be placed in the Content-Description header field. This header
field is always optional.
...
... image" body as "a picture of the Space Shuttle Endeavor." Such text
may be placed in the Content-Description header field. This header
field is always optional.
...
... Future documents may elect to define additional MIME header fields
for various purposes. Any new header field that further describes
the content of a message should begin with the string "Content-" to
allow such fields which appear in a message header ...
... Content-Type, and Content-Transfer-Encoding
header fields, it is possible to include, in a standardized way,
arbitrary types of data with RFC 822std11(-> 2822prop) conformant mail messages ...
... fields version CRLF ; The ordering of the header fields implied by this BNF definition should be ignored. ...
... entity-headers [fields] ; Any field not beginning with "content-" can have no defined meaning and may be ignored. The ordering of the header fields implied by this BNF definition should be ignored. ...