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Multi-purpose Internet Multi-purpose Internet

Mail ExtensionMail Extension (MIME)(MIME)



MIME:

ContentsContents

Definition of MIME

Introduction

What exactly is MIME?

How it Works?

MIME-Specific Technical DefinitionsExample of MIME

Summary



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. ”



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.



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.



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.



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.



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



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.



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.



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



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



MIME:

New MIME headersNew MIME headers

Required fields

MIME - VersionDate - Time

Optional fields

Content- typeContent-transfer_encoding

Content-ID

Content-descriptionContent-disposition



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



MIME:

The Content-type ApplicationsThe Content-type Applications

Subtypes:

Postscript Octet-Stream-Unidentified binary

data

Many other will be added



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



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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