MIME's use, however, has grown beyond describing the content of e-mail Electronic mail, most commonly abbreviated email or e-mail, is a method of exchanging digital messages. E-mail systems are based on a store-and-forward model in which e-mail server computer systems accept, forward, deliver and store messages on behalf of users, who only need to connect to the e-mail infrastructure, typically an e-mail server, with to describing content type in general, including for the web (see Internet media type An Internet media type, originally called a MIME type after MIME and sometimes a Content-type after the name of a header in several protocols whose value is such a type, is a two-part identifier for file formats on the Internet. The identifiers were originally defined in RFC 2046 for use in e-mail sent through SMTP, but their use has expanded to).
Virtually all human-written Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and e-mail and a fairly large proportion of automated e-mail is transmitted via SMTP Simple Mail Transfer Protocol is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. SMTP was first defined in RFC 821 (STD 15) (1982), and last updated by RFC 5321 (2008) which includes the extended SMTP (ESMTP) additions, and is the protocol in widespread use today. SMTP is specified for in MIME format. Internet e-mail is so closely associated with the SMTP and MIME standards that it is sometimes called SMTP/MIME e-mail.[1]
The content types defined by MIME standards are also of importance outside of e-mail, such as in communication protocols In computing and telecommunications, a protocol or communications protocol is a formal description of message formats and the rules for exchanging those messages. Protocols may include signaling, authentication and error detection and correction capabilities. In its simplest form, a protocol can be defined as the rules governing the syntax, like HTTP The Hypertext Transfer Protocol is an Application Layer protocol for distributed, collaborative, hypermedia information systems for the World Wide Web The World Wide Web, abbreviated as WWW and commonly known as the Web, is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them by using hyperlinks. Using concepts from earlier hypertext systems, British. HTTP requires that data be transmitted in the context of e-mail-like messages, although the data most often is not actually e-mail.
MIME is specified in six linked RFC memoranda In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force (IETF) describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems: RFC 2045, RFC 2046, RFC 2047, RFC 4288, RFC 4289 and RFC 2049, which together define the specifications.
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Introduction
The basic Internet e-mail transmission protocol, SMTP, supports only 7-bit ASCII The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text. Most modern character-encoding schemes are based on ASCII, though they support many more characters than did ASCII characters (see also 8BITMIME Extended SMTP , sometimes referred to as Enhanced SMTP, is a definition of protocol extensions to the Simple Mail Transfer Protocol standard. The extension format was defined in IETF publication RFC 1869 (1995) which established a general structure for all existing and future extensions). This effectively limits Internet e-mail to messages which, when transmitted, include only the characters sufficient for writing a small number of languages, primarily English English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into South-East Scotland under the influence of the Anglian medieval kingdom of Northumbria. Following the economic, political, military, scientific, cultural, and colonial influence of Great Britain and the United Kingdom from the 18th century, via. Other languages based on the Latin alphabet The Latin alphabet, also called the Roman alphabet, is the most widely used alphabetic writing system in the world today. It evolved from the western variety of the Greek alphabet called the Cumaean alphabet, which was borrowed and modified by the Etruscans who ruled early Rome, whose alphabet was then adapted and further modified by the ancient typically include diacritics A diacritic (also diacritical mark, diacritical point, diacritical sign) is an ancillary glyph added to a letter, or basic glyph. The term derives from the Greek διακριτικός (diakritikós, "distinguishing"). Diacritic is both an adjective and a noun, whereas diacritical is only an adjective. Some diacritical marks, such as the not supported in 7-bit ASCII, meaning text in these languages cannot be correctly represented in basic e-mail.
MIME defines mechanisms for sending other kinds of information in e-mail. These include text in languages other than English using character encodings A character encoding system consists of a code that pairs each character from a given repertoire with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the transmission of data through telecommunication networks or storage of text in computers other than ASCII, and 8-bit binary content such as files containing images An image is an artifact, for example a two-dimensional picture, that has a similar appearance to some subject—usually a physical object or a person, sounds Sound is a travelling wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations, movies A film, also called a movie or motion picture, is a story conveyed with moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects. The process of filmmaking has developed into an art form and industry, and computer programs A computer program is a sequence of instructions written to perform a specified task for a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-. MIME is also a fundamental component of communication protocols such as HTTP The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, which requires that data be transmitted in the context of e-mail-like messages even though the data might not (and usually doesn't) actually have anything to do with e-mail. Mapping messages into and out of MIME format is typically done automatically by an e-mail client An email client, email reader, or more formally mail user agent , is a computer program used to manage a user's email or by mail servers Within Internet message handling services , a message transfer agent or mail transfer agent (MTA) or mail relay is a computer process or software agent that transfers electronic mail messages from one computer to another, in single hop application-level transactions. An MTA implements both the client (sending) and server (receiving) portions of when sending or receiving Internet (SMTP/MIME) e-mail.
The basic format of Internet e-mail is defined in RFC 5322, which is an updated version of RFC 2822 and RFC 822. These standards specify the familiar formats for text e-mail headers In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body and body and rules pertaining to commonly used header fields such as "To:", "Subject:", "From:", and "Date:". MIME defines a collection of e-mail headers for specifying additional attributes of a message including content type, and defines a set of transfer encodings which can be used to represent 8-bit binary data using characters from the 7-bit ASCII character set. MIME also specifies rules for encoding non-ASCII characters in e-mail message headers, such as "Subject:", allowing these header fields to contain non-English characters.
MIME is extensible. Its definition includes a method to register new content types and other MIME attribute values.
The goals of the MIME definition included requiring no changes to existent e-mail servers and allowing plain text e-mail to function in both directions with existing clients. These goals were achieved by using additional RFC 822-style headers for all MIME message attributes and by making the MIME headers optional with default values ensuring a non-MIME message is interpreted correctly by a MIME-capable client. A simple MIME text message is therefore likely to be interpreted correctly by a non-MIME client although if it has e-mail headers the non-MIME client won't know how to interpret. Similarly, if the quoted printable transfer encoding (see below) is used, the ASCII part of the message will be intelligible to users with non-MIME clients.
MIME headers
MIME-Version
The presence of this header indicates the message is MIME-formatted. The value is typically "1.0" so this header appears as
MIME-Version: 1.0
It should be noted that implementers have attempted to change the version number in the past and the change had unforeseen results.[citation needed] It was decided at an IETF The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite. It is an open standards organization, with no formal membership or membership requirements. All participants and managers are meeting[2] to leave the version number as is even though there have been many updates and versions of MIME.
Content-ID
The Content-ID header is primarily of use in multi-part messages (as discussed below); a Content-ID is a unique identifier for a message part, allowing it to be referred to (e.g., in IMG tags of an HTML message allowing the inline display of attached images). The content ID is contained within angle brackets in the Content-ID header. Here is an example:
Content-ID: <5.31.32252.1057009685@server01.example.net>
The standards don't really have a lot to say about exactly what is in a Content-ID; they're only supposed to be globally and permanently unique (meaning that no two are the same, even when generated by different people in different times and places). To achieve this, some conventions have been adopted; one of them is to include an at sign (@), with the hostname of the computer which created the content ID to the right of it. This ensures the content ID is different from any created by other computers (well, at least it is when the originating computer has a unique Internet hostname; if, as sometimes happens, an anonymous machine inserts something generic like localhost, uniqueness is no longer guaranteed). Then, the part to the left of the at sign is designed to be unique within that machine; a good way to do this is to append several constantly-changing strings that programs have access to. In this case, four different numbers were inserted, with dots between them: the rightmost one is a timestamp of the number of seconds since January 1, 1970, known as the Unix epoch; to the left of it is the process ID of the program that generated the message (on servers running Unix or Linux, each process has a number which is unique among the processes in progress at any moment, though they do repeat over time); to the left of that is a count of the number of messages generated so far by the current process; and the leftmost number is the number of parts in the current message that have been generated so far. Put together, these guarantee that the content ID will never repeat; even if multiple messages are generated within the same second, they either have different process IDs or a different count of messages generated by the same process.
That's just an example of how a unique content ID can be generated; different programs do it differently. It's only necessary that they remain unique, a requirement that is necessary to ensure that, even if a bunch of different messages are joined together as part of a bigger multi-part message (as happens when a message is forwarded as an attachment, or assembled into a MIME-format digest), you won't have two parts with the same content ID, which would be likely to confuse mail programs greatly.
There's a similar header called Message-ID which assigns a unique identifier to the message as a whole; this is not actually part of the MIME standards, since it can be used on non-MIME as well as MIME messages. If the originating mail program doesn't add a message ID, a server handling the message later on probably will, since a number of programs (both clients and servers) want every message to have one in order to keep track of them. Some headers discussed in the Other Headers article make use of message IDs.
When referenced in the form of a Web URI In computing, a Uniform Resource Identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network (typically the World Wide Web) using specific protocols. Schemes specifying a concrete syntax and associated protocols define each (the term "URL In computing, a Uniform Resource Locator is a Uniform Resource Identifier (URI) that specifies where an identified resource is available and the mechanism for retrieving it. In popular usage and in many technical documents and verbal discussions it is often incorrectly used as a synonym for URI. The best-known example of a URL is the "address&" is being deprecated by the newest proposed Web standards in favor of "URI"), content IDs and message IDs are placed within the URI schemes cid and mid respectively, without the angle brackets:
cid:5.31.32252.1057009685@server01.example.net
Content-Type
This header indicates the Internet media type An Internet media type, originally called a MIME type after MIME and sometimes a Content-type after the name of a header in several protocols whose value is such a type, is a two-part identifier for file formats on the Internet. The identifiers were originally defined in RFC 2046 for use in e-mail sent through SMTP, but their use has expanded to of the message content, consisting of a type and subtype, for example
Content-Type: text/plain
Through the use of the multipart type, MIME allows messages to have parts arranged in a tree structure A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, even though the chart is generally upside down compared to an actual tree, with the "root" at the top and the "leaves" at the bottom where the leaf nodes are any non-multipart content type and the non-leaf nodes are any of a variety of multipart types. This mechanism supports:
- simple text messages using text/plain (the default value for "Content-Type: ")
- text plus attachments (multipart/mixed with a text/plain part and other non-text parts). A MIME message including an attached file generally indicates the file's original name with the "Content-disposition:" header, so the type of file is indicated both by the MIME content-type and the (usually OS An operating system is the software on a computer that manages the way different programs use its hardware, and regulates the ways that a user controls the computer. Operating systems are found on almost any device that contains a computer with multiple programs—from cellular phones and video game consoles to supercomputers and web servers. Some-specific) filename extension A filename extension is a suffix to the name of a computer file applied to indicate the encoding convention of its contents
- reply with original attached (multipart/mixed with a text/plain part and the original message as a message/rfc822 part)
- alternative content, such as a message sent in both plain text and another format such as HTML HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. It is written in the form of HTML elements consisting of "tags" surrounded by angle brackets within the web page content (multipart/alternative with the same content in text/plain and text/html forms)
- image, audio, video and application (for example, image/jpg, audio/mp3, video/mp4, and application/msword and so on)
- many other message constructs
Content-Disposition
The original MIME specifications only described the structure of mail messages. They did not address the issue of presentation styles. The content-disposition header field was added in RFC 2183 to specify the presentation style. A MIME part can have:
- an inline content-disposition, which means that it should be automatically displayed when the message is displayed, or
- an attachment content-disposition, in which case it is not displayed automatically and requires some form of action from the user to open it.
In addition to the presentation style, the content-disposition header also provides fields for specifying the name of the file, the creation date and modification date, which can be used by the reader's mail user agent to store the attachment.
The following example is taken from RFC 2183, where the header is defined
Content-Disposition: attachment; filename=genome.jpeg; modification-date="Wed, 12 Feb 1997 16:29:51 -0500";
The filename may be encoded as defined by RFC 2231.
As of 2010, a good majority of mail user agents An email client, email reader, or more formally mail user agent , is a computer program used to manage email do not follow this prescription fully. The widely used Mozilla Thunderbird Mozilla Thunderbird is a free, open source, cross-platform e-mail and news client developed by the Mozilla Foundation. The project strategy is modeled after Mozilla Firefox, a project aimed at creating a web browser. On December 7, 2004, version 1.0 was released, and received over 500,000 downloads in its first three days of release, and 1,000,000 mail client makes its own decisions about which MIME parts should be automatically displayed, ignoring the content-disposition headers in the messages. It also sends out newly composed messages with inline content-disposition for all MIME parts. Most users are unaware of how to set the content-disposition to attachment.[4] Many mail user agents also send messages where they put the file name in the name parameter of the content-type header instead of the filename parameter of the content-disposition header. This practice is discouraged.[5]
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This setback happens when there is no MIME (. Multipurpose Internet Mail Extensions. ) type registered for the PPS files. Since the PPS is linked with PowerPoint, Microsoft Internet Explorer routes the file as a PPT (PowerPoint ...
Q. please help wikipedia says that it stands for Multipurpose Internet Mail Extensions, but not how to open one...
Asked by Whitnae - Thu Jan 4 18:33:08 2007 - - 1 Answers - 0 Comments
A. Are you using aol mail? Try to downlod the file and unzip it.
Answered by tast_the_wine - Thu Jan 4 18:40:33 2007
