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Multi-purpose Internet

Mail Extension (MIME)



MIME:

Definition of MIME

“MIME, stand for Multi-purpose Internet mail

Extensions , is a freely available specification thatoffers a way to interchange text in languages withdifferent character sets, and multimedia e-mailamong many different computer system that use

Internet mail standards. ”



MIME:

Introduction

MIME extends the format of Internet mail to allow non-US-ASCII textual messages, non-textual messages,multipart message bodies, and non-US-ASCIIinformation in message headers.

MIME provides Internet mail users with functionalitysimilar to that of MS-Mail for LAN-based internal mail.MS-Mail and MIME allow the attachment of files andother objects, as does MIME. Unfortunately,Microsoft’s method of handling these attachments is

undertaken through a proprietary format and MS-Maildoes not provide compliance with the MIME open

standard.



MIME:

Cont……

Internet messages with MIME attachments send to MS-Mail will transfer the appropriate text portions of themessage, but MS-Mail will generally forward theattachments as encoded text, which may then be

saved to a file and decoded. Conversely, messagessent from MS-Mail with attachments to an InternetMIME mail system will transfer the text portions andsend the attachments as encoding text, but use a

different method of encoding from the used by MIMEand without the information needed for processing themessage attachment by the recipient. Email messagesarriving at the National Library with MIME attachmentsare likely to be corrupted.



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… MIME is a specification for enhancing the

capabilities of standard Internet e-mail.

It offers a simple standardized way to representand encode a wide variety of media types oftransmission via Internet mail.

It is defines extensions to SMTP to supportbinary 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… When using the MIME standard, messages can

contain the following types:

Text message in US-ASCII

Character set other than US-ASCII

Multiple objects in a single messages

Multimedia; Image, Audio, and Video messages

Multi-front messages

Messages of unlimited length

Binary files



MIME:

Cont…

MIME is defined to be completely backwardscompatible, yet flexible and open to

extensions. Therefore, it builds on theolder standard by defining additionalfields for the mail message header, thatdescribes new content types, and a

distinct organization of the message body.



MIME:

How MIME works?

The developers of MIME found a clever way towork around the limitation. It packages differentdata 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…

Uses a new binary encoding scheme calledBASE 64

New SMTP headers describe the attached

document

User agents read the header to figure out howto interpret the message



MIME:

MIME Specific technical definition

New MIME headers

The Content-type headers

The Application-type headers

The Content-transfer-Encoding The Content-ID &Content Description

Multipart Message

Non-ASCII text in mail messages



MIME:

New MIME headers

Required fields

MIME - Version Date - Time

Optional fields

Content- type Content-transfer_encoding

Content-ID

Content-description Content-disposition



MIME:

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 Applications

Subtypes:

Postscript Octet-Stream-Unidentified binary

data

Many other will be added



MIME:

The Content-transfer-Encoding

Base64 encoding algorithm is used to encodebinary 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:

Summary

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 ofdifferent types in a single message. Furthercontent 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 useragents, notably Text/Richtext, Message/Partial,

and Message/External-Body.

mime final ppt

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