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header field
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1. A MIME-Version header field, which uses a version number to
declare a message to be conformant with this specification and
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3. A Content-Transfer-Encoding header field, which can be used to
specify an auxiliary encoding that was applied to the data in
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... The MIME-Version Header Field ...
... message was composed with the new standard in mind.
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:
MIME-Version ...
... MIME-Version: 1.0
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
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NOTE TO IMPLEMENTORS: All header fields defined in this document,
including MIME-Version, Content-type ...
... Content-type, etc., are subject to the
general syntactic rules for header fields specified in RFC 822std11(-> 2822prop). In
particular, all can include comments, which means that the following
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... The Content-Type Header Field ...
...
HISTORICAL NOTE: The Content-Type header field was first defined in
RFC 1049hist. RFC 1049hist ...
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The Content-Type header field is used to specify the nature of the
data in the body of an entity, by giving type and subtype
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... required for certain types. After the type and subtype names, the
remainder of the header field is simply a set of parameters,
specified in an attribute/value notation. The set of meaningful
parameters differs for the different types. In particular, there are
...
... Global mechanisms are best addressed, in the MIME model, by the
definition of additional Content-* header fields. The ordering of
parameters is not significant. Among the defined parameters is a
"charset ...
... be declared. Comments are allowed in accordance with RFC 822std11(-> 2822prop) rules
for structured header fields.
In general, the top-level ...
... Augmented BNF notation of RFC 822std11(-> 2822prop), a Content-Type header field
value is defined as follows:
...
... 822std11(-> 2822prop) conformant message which
may contain its own different Content-Type header
field. The primary subtype is "rfc822". The
"partial" subtype is defined for partial messages,
to permit the fragmented transmission of bodies
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... header field or
MIME-Version header field, it is impossible to be certain that a
message is actually text in the US-ASCII character set ...
... MIME-Version and the
Content-Type header fields, it may in practice contain almost
anything.
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... The Content-Transfer-Encoding Header Field ...
... encodings will be indicated by a new "Content-
Transfer-Encoding" header field. The Content-Transfer-Encoding field
is used to indicate the type of transformation that has been used in
...
... Content-Transfer-Encoding: 7BIT" is
assumed if the Content-Transfer-Encoding header field is not present.
The values "8bit ...
...
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 a body
part's headers, it applies only to the body of that body part. If an
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... Additional Content-Header Fields ...
... Optional Content-ID Header Field ...
... one body to make reference to another. Accordingly, bodies may be
labeled using the "Content-ID" header field, which is syntactically
identical to the "Message-ID" header field ...
... header field, which is syntactically
identical to the "Message-ID" header field:
id := "Content-ID ...
... Optional 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.
description := "Content-Description" ":" *text
...
... specify a character set via the Content-Type header field. "US-
ASCII" does not indicate an arbitrary seven-bit ...
...
The formal grammar for the content-type header field for text is as
follows:
...
... 822std11(-> 2822prop)
message. To begin with, NO header fields are actually required in
body parts. A body part that starts with a blank line, therefore, is
...
... default values are to be
assumed. In such a case, the absence of a Content-Type header field
implies that the corresponding body is plain US-ASCII text. The only
...
... implies that the corresponding body is plain US-ASCII text. The only
header fields that have defined meaning for body parts are those the
names of which begin with "Content-". All other header fields are
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... encapsulated message, with its own "Content-Type: image" 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 ...
... encoding other than "7bit", "8bit", or "binary" is permitted for
entities of type "multipart". The multipart delimiters and header
fields are always represented as 7-bit ASCII in any case (though the
...
... 7-bit ASCII in any case (though the
header fields may encode non-ASCII header text as per [RFC-1522 ...
... parameter value from the Content-Type header field.
NOTE: The hyphens are for rough compatibility ...
... Content-type
fields. Thus, a typical multipart Content-Type header field might
look like this:
...
... preceding part. The boundary must be followed immediately either by
another CRLF and the header fields for the next part, or by two
CRLFs, in which case there are no header fields for the next part
...
... CRLF and the header fields for the next part, or by two
CRLFs, in which case there are no header fields for the next part
(and it is therefore assumed to be of Content-Type text/plain ...
... body-part := <"message" as defined in RFC 822std11(-> 2822prop),
with all header fields optional, and with the
specified delimiter not occurring anywhere in
the message body ...
...
Content-Transfer-Encoding header field. However, in no event are
headers (either message headers ...
...
The formal grammar for content-type header fields for multipart data
is given by:
...
... any case, and data within the body can still be encoded, in which
case the Content-Transfer-Encoding header field in the encapsulated
message will reflect this. Non-ASCII ...
... 822std11(-> 2822prop) message. In
particular, they frequently add, remove, or reorder header fields.
Such alterations are explicitly forbidden for the encapsulated
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...
Thus, part 2 of a 3-part message may have either of the following
header fields:
Content-Type ...
... entity, which may have its
own Content-Type header field, and thus may contain any other data
type.
...
... rules must be observed:
(1) All of the header fields from the initial enclosing entity
(part one), except those that start ...
... (part one), except those that start with "Content-" and the
specific header fields "Message-ID", "Encrypted", and "MIME ...
... Version", must be copied, in order, to the new message.
(2) Only those header fields in the enclosed message which start
with "Content-" and "Message-ID ...
... Encrypted", and "MIME-Version"
must be appended, in order, to the header fields of the new
message. Any header fields in the enclosed message which do not
...
... must be appended, in order, to the header fields of the new
message. Any header fields in the enclosed message which do not
start with "Content-" (except for "Message-ID ...
... MIME-Version") will be ignored.
(3) All of the header fields from the second and any subsequent
messages will be ignored.
...
...
Finally, it should be noted that the "Encrypted" header field has
been made obsolete by Privacy Enhanced Messaging (PEM ...
... message/external-body entities MUST
include a Content-ID header field to give a unique identifier by
...
... message/external-body", then the body of the
entity will contain the header fields of the encapsulated message.
The body itself is to be found in the external location. This means
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... place for additional data that cannot be included in the content-type
header field. In particular, if the "access-type" value is "mail-
server", then the trailing area must contain commands to be sent to
the mail server at the address ...
...
The formal grammar for content-type header fields for data of type
message is given by:
...
... file. This has been deprecated in anticipation of a separate
Content-Disposition header field, to be defined in a subsequent RFC.
The recommended action for an implementation that receives
...
...
The formal grammar for the content-type header field for data of type
video is given by:
...
... Content-Type, and Content-Transfer-Encoding
header fields, it is possible to include, in a standardized way,
arbitrary types of data objects with RFC 822std11(-> 2822prop) ...
... distinguished parameter syntax allows further specification of data
format details, particularly the specification of alternate character
sets. Additional optional header fields provide mechanisms for
certain extensions deemed desirable by many implementors. Finally, a
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...
1. Always generate a "MIME-Version: 1.0" header field.
2. Recognize the Content-Transfer-Encoding ...
...
2. Recognize the Content-Transfer-Encoding header field, and
decode all received data encoded with either the quoted-printable
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...
3. Recognize and interpret the Content-Type header field, and
avoid showing users raw data with a Content-Type field other than
...
... ...Some text appears here...
[Note that the preceding blank line means
no header fields were given and this is text,
with charset US ASCII ...
... body-part := <"message" as defined in RFC 822std11(-> 2822prop),
with all header fields optional, and with the
specified delimiter not occurring anywhere in
the message body ...
... transport and adequately documented in the
Content-Transfer-Encoding header field. However, in no event are
headers (either message headers ...
...
In general, parameters in the content-type header field are used to
convey supplemental information for various content types, and their
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... the resulting messages must be consistent with those produced by the
model described here. For example, a message with the following
header fields:
Content-type ...