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Multi-purpose Internet Multi-purpose Internet
Mail ExtensionMail Extension (MIME)(MIME)
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MIME:
ContentsContents
Definition of MIME
Introduction
What exactly is MIME?
How it Works?
MIME-Specific Technical DefinitionsExample of MIME
Summary
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MIME:
Definition of MIMEDefinition of MIME
“MIME, stand for Multi-purpose Internet mail
Extensions, is a freely available specification thatoffers a way to interchange text in languages with
different character sets, and multimedia e-mail
among many different computer system that use
Internet mail standards. ”
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MIME:
IntroductionIntroduction
MIME extends the format of Internet mail to allownon-US-ASCII textual messages, non-textual
messages, multipart message bodies, and
non-US-ASCII information in message headers.
MIME provides Internet mail users with functionality
similar to that of MS-Mail for LAN-based internal mail.
MS-Mail and MIME allow the attachment of files and
other objects, as does MIME. Unfortunately,
Microsoft’s method of handling these attachments is
undertaken through a proprietary format and MS-Mail
does not provide compliance with the MIME open
standard.
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MIME:
Cont……Cont……
Internet messages with MIME attachments send toMS-Mail will transfer the appropriate text portions of
the message, but MS-Mail will generally forward the
attachments as encoded text, which may then be
saved to a file and decoded. Conversely, messagessent from MS-Mail with attachments to an Internet
MIME mail system will transfer the text portions and
send the attachments as encoding text, but use a
different method of encoding from the used by MIMEand without the information needed for processing the
message attachment by the recipient. Email messages
arriving at the National Library with MIME attachments
are likely to be corrupted.
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MIME:
What exactly is MIME?What exactly is MIME? In 1992, a new standard was defined by an
Internet engineering task force working group inRFC1521 & 1522 called MIME.
MIME is an extension to the Internet mail standard,known as Simple Mail Transfer Protocol (SMTP)that allows mail messages containing differenttype of multimedia information to be sent acrossthe network this includes, but is not limited to,word-processor documents, spreadsheets,programs, graphics, audio, and motion picturefiles, as well as links that enable users to retrieveinformation from remote databases from within a
mail message.
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MIME:
Cont…Cont…MIME is a specification for enhancing the
capabilities of standard Internet e-mail.
It offers a simple standardized way to represent
and encode a wide variety of media types of
transmission via Internet mail.
It is defines extensions to SMTP to support
binary attachments of arbitrary format.
The designers of MIME have learned a lot fromthe old SMTP protocol and its mailers.
MIME is here to stay and it works.
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MIME:
Cont…Cont…When using the MIME standard, messages can
contain the following types:
Text message in US-ASCII
Character set other than US-ASCIIMultiple objects in a single messages
Multimedia; Image, Audio, and Video messages
Multi-front messages
Messages of unlimited length
Binary files
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MIME:
Cont…Cont…
MIME is defined to be completely backwards
compatible, yet flexible and open to
extensions. Therefore, it builds on theolder standard by defining additional
fields for the mail message header, that
describes new content types, and a
distinct organization of the message body.
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MIME:
How MIME works?How MIME works?
The developers of MIME found a clever way to
work around the limitation. It packages different
data types into a 7-bit ASCII format. that way, all
e-mail, regardless of the data it contains, appearsas standard e-mail messages to the internet’s
SMTP servers. The beauty of the solution lies in
the fact that SMTP didn’t have to change to
handle such data.
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MIME:
Cont…Cont…
Uses a new binary encoding scheme called
BASE 64
New SMTP headers describe the attached
documentUser agents read the header to figure out how
to interpret the message
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MIME:
MIME Specific technical definitionMIME Specific technical definition
New MIME headers
The Content-type headers
The Application-type headers
The Content-transfer-EncodingThe Content-ID &Content Description
Multipart Message
Non-ASCII text in mail messages
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MIME:
New MIME headersNew MIME headers
Required fields
MIME - VersionDate - Time
Optional fields
Content- typeContent-transfer_encoding
Content-ID
Content-descriptionContent-disposition
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MIME:
The Content-type Header The Content-type Header Content-type sub-type describes what format
this part of the message is in
Text Image
Message AudioApplication Video
Multipart
The default type is simple ASCII text
MIME-Version : 1.0
Content-type:text/plain;charset=US-ascii
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MIME:
The Content-type ApplicationsThe Content-type Applications
Subtypes:
Postscript Octet-Stream-Unidentified binary
data
Many other will be added
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MIME:
The Content-transfer-EncodingThe Content-transfer-Encoding
Base64 encoding algorithm is used to encode
binary data in 7bit ASCII data
Quoted-printable is for text-only messages
A few others
7bit No encoding Case insensitive
8bit No encoding
Binary No encodingX-token No encoding
Example
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MIME:
SummarySummary
MIME has been designed to avoid problemscaused by additional restrictions imposed bysome Internet mail transport mechanisms.
The Multipart and Message content types allow
mixing and hierarchical structuring of objects of different types in a single message. Further content types provide a mechanism for taggingmessages or body parts as audio, image, or
other kinds of data.Finally, a number of useful content types are
defined for general use by consenting user agents, notably Text/Richtext, Message/Partial,
and Message/External-Body.
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