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Encyclopedia > Electronic mail

Electronic mail, abbreviated e-mail or email, is a method of composing, sending, and receiving messages over electronic communication systems. Most e-mail systems today use the Internet. Look up Electronic in Wiktionary, the free dictionary Electronic can refer to many things: Objects related to electronics The band Electronic. ... The Internet, or simply the Net, is the publicly available worldwide system of interconnected computer networks that transmit data by packet switching using a standardized Internet Protocol (IP) and many other protocols. ...

Contents

Origins of e-mail

Despite common belief, e-mail actually pre-dates the Internet; in fact, existing e-mail systems were a crucial tool in creating the Internet.


E-mail started in 1965 as a way for multiple users of a time-sharing mainframe computer to communicate. Although the exact history is murky, among the first systems to have such a facility were SDC's Q32 and MIT's CTSS. 1965 was a common year starting on Friday (the link is to a full 1965 calendar). ... Alternate uses: see Timesharing Time-sharing is an approach to interactive computing in which a single computer is used to provide apparently simultaneous interactive general-purpose computing to multiple users by sharing processor time. ... Mainframes (often colloquially referred to as big iron) are large and expensive computers used mainly by government institutions and large companies for legacy applications, typically bulk data processing (such as censuses, industry/consumer statistics, ERP, and bank transaction processing). ... System Development Corporation, based in Los Angeles, California, was spun off from RAND Corporation in 1957. ... Q32 (ANFSQ-32) was a computer made by IBM (International Business Machines) in 1960 and 1961 for the Unites States Air Force Strategic Air Command (SAC). ... MIT redirects here. ... This article is about the MIT Project MAC operating system. ...


E-mail was quickly extended to become network e-mail, allowing users to pass messages between different computers. The early history of network e-mail is also murky; the AUTODIN system may have been the first allowing electronic text messages to be transferred between users on different computers in 1966, but it is possible the SAGE system had something similar some time before. The Automatic Digital Network (AUTODIN) is a legacy data communications service in the United States Department of Defense. ... -1... This article is about the sage plant; for other uses see Sage (disambiguation) Species Salvia aethiopis L. Salvia amissa Epling Salvia apiana Jepson Salvia argentea L. Salvia arizonica Gray Salvia azurea Michx. ...


The ARPANET computer network made a large contribution to the evolution of e-mail. There is one report [1]  (http://www.multicians.org/thvv/mail-history.html) which indicates experimental inter-system e-mail transfers on it shortly after its creation, in 1969. Ray Tomlinson initiated the use of the @ sign to separate the names of the user and their machine in 1971 [2]  (http://openmap.bbn.com/~tomlinso/ray/firstemailframe.html). The common report that he "invented" e-mail is an exaggeration, although his early e-mail programs SNDMSG and READMAIL were very important. The ARPANET significantly increased the popularity of e-mail, and it became the killer app of the ARPANET. ARPANET logical map, March 1977. ... A computer network is a system for communication among two or more computers. ... 1969 was a common year starting on Wednesday (the link is to a full 1969 calendar). ... Raymond Tomlinson (born 1941) is a programmer who first used the @ symbol for sending email in 1972. ... Not to be confused with commercial art. ... 1971 is a common year starting on Friday (click for link to calendar). ... SNDMSG was one component of a mail program written by Ray Tomlinson that was first used in 1971 for TENEX. The other component was READMAIL. SNDMSG was used for the purpose of sending Electronic Mail from one user to another, however, it was not capable of sending to different machines. ... A killer application (commonly shortened to killer app) is a computer program that is so useful that people will buy a particular computer hardware, gaming console, and/or an operating system simply to run that program. ...


Growing popularity

As the utility and advantages of e-mail on the ARPANET became more widely known, the popularity of e-mail increased, leading to demand from people who were not allowed access to the ARPANET. A number of protocols were developed to deliver e-mail among groups of time-sharing computers over alternative transmission systems, such as UUCP and IBM's VNET e-mail system. UUCP stands for Unix to Unix Copy Protocol, and is a computer program and protocol allowing remote execution of commands and transfer of files, email and netnews between Unix computers not connected to the Internet proper. ... International Business Machines Corporation (IBM, or colloquially, Big Blue) (NYSE: IBM) (incorporated June 15, 1911, in operation since 1888) is headquartered in Armonk, New York, USA. The company manufactures and sells computer hardware, software, and services. ... VNET was a corporate email system from IBM (1988). ...


Since not all computers or networks were directly inter-networked, e-mail addresses had to include the "route" of the message, that is, a path between the computer of the sender and the computer of the receivers. E-mail could be passed this way between a number of networks, including the ARPANET, BITNET and NSFNET, as well as to hosts connected directly to other sites via UUCP. The tower of a personal computer (specifically a Power Mac G5). ... A wide variety of systems of interconnected components are called networks. ... ARPANET logical map, March 1977. ... BITNET was a cooperative U.S. university network founded in 1981 under the aegis of Ira Fuchs and Greydon Freeman at the City University of New York (CUNY). ... National Science Foundation Network (NSFNet) was a major part of early 1990s Internet backbone. ...


The route was specified using so-call "bang path" addresses, specifying hops to get from some assumed-reachable location to the addressee, so called because each hop is signified by a "bang sign" (the exclamation mark, !). Thus, for example, the path ...!bigsite!foovax!barbox!me directs people to route their mail to machine bigsite (presumably a well-known location accessible to everybody) and from there through the machine foovax to the account of user me on barbox. An exclamation mark (also exclamation point, and (rarely) mark of admiration) is a punctuation mark or, more pedantically, a tone mark. ...


Before auto-routing mailers became commonplace, people often published compound bang addresses using the { } convention (see glob) to give paths from several big machines, in the hopes that one's correspondent might be able to get mail to one of them reliably (example: ...!{seismo, ut-sally, ihnp4}!rice!beta!gamma!me). Bang paths of 8 to 10 hops were not uncommon in 1981. Late-night dial-up UUCP links would cause week-long transmission times. Bang paths were often selected by both transmission time and reliability, as messages would often get lost. glob() is a Unix library function that expands file paths according to a minimal regular expression syntax. ... 1981 is a common year starting on Thursday. ...


Modern Internet e-mail

How e-mail works

How e-mail works

The diagram above shows a stereotypical sequence of events that takes place when Alice sends an e-mail to Bob. How e-mail works File links The following pages link to this file: Electronic mail User:Gdr/Gallery Categories: GFDL images ...

  1. Alice composes a message using her mail user agent (MUA). She types in, or selects from an address book, the e-mail address of her correspondent. She hits the "send" button and the MUA uses the Simple Mail Transfer Protocol (SMTP) to send the message to the local mail transfer agent (MTA), in this case smtp.a.org, run by Alice's Internet Service Provider (ISP).
  2. The MTA looks at the destination address, in this case [email protected]. A modern Internet e-mail address is a string of the form [email protected]. The part before the @ sign is the local part of the address, often the username of the recipient, and the part after the @ sign is a domain name. The MTA looks up this domain name in the Domain Name System to find the mail exchange servers accepting messages for that domain.
  3. The DNS server for the b.org domain, ns.b.org, responds with an MX record listing the mail exchange servers for that domain, in this case mx.b.org, a server run by Bob's ISP.
  4. smtp.a.org sends the message to mx.b.org using SMTP, which delivers it to the mailbox of the user bob.
  5. Bob presses the "get mail" button in his MUA, which picks up the message using the Post Office Protocol (POP3).

This sequence of events probably applies to the majority of e-mail users. However, there are many alternative possibilities and complications to the e-mail system: An email client (or mail user agent [MUA]) is a computer program that is used to read and send email. ... Simple Mail Transfer Protocol (SMTP) is the de facto standard for email transmission across the Internet. ... A mail transfer agent or MTA (also called a mail server, or a mail exchange server in the context of the Domain Name System) is a computer program or software agent which transfers electronic mail messages from one computer to another. ... An Internet Service Provider (ISP) is a business or organization that offers users access to the Internet and related services. ... Note: to create a user account for Wikipedia, go to the login page. ... A domain name is the unique name of a computer on the Internet that distinguishes it from the other systems on the network. ... The Domain Name System or DNS is a system that stores information about host names and domain names in a kind of distributed database on networks, such as the Internet. ... A mail transfer agent or MTA (also called a mail server, or a mail exchange server in the context of the Domain Name System) is a computer program or software agent which transfers electronic mail messages from one computer to another. ... The Domain Name System or DNS is a system that stores information about host names and domain names in a kind of distributed database on networks, such as the Internet. ... An MX record or Mail exchange record is a category of data in the Domain Name System specifying how Internet e-mail should be routed. ... Post Office Protocol version 3 (POP3) is an application layer Internet standard protocol used to retrieve email from a remote server to a local client over a TCP/IP connection. ...

  • Alice may not have a MUA on her computer but instead may connect to a webmail service.
  • Alice's computer may run its own MTA, so avoiding the transfer at step 1.
  • Bob may pick up his e-mail in many ways, for example using the Internet Message Access Protocol, by logging into mx.b.org and reading it directly, or by using a webmail service.
  • Domains usually have several mail exchange servers so that they can continue to accept mail when the main mail exchange server is not available.

It used to be the case that many MTAs would accept messages for any recipient on the Internet and do their best to deliver them. Such MTAs are called open mail relays. This was important in the early days of the Internet when network connections were unreliable. If an MTA couldn't reach the destination, it could at least deliver it to a relay that was closer to the destination. The relay would have a better chance of delivering the message at a later time. However, this mechanism proved to be exploitable by people sending unsolicited bulk e-mail and as a consequence very few modern MTAs are open mail relays, and many MTAs will not accept messages from open mail relays because such messages are very likely to be spam. Webmail is a World Wide Web interface that allows users to read and write E-mail using a Web browser. ... The Internet Message Access Protocol (commonly known as IMAP, and previously called Interactive Mail Access Protocol) is an application layer Internet protocol used for accessing email on a remote server from a local client. ... Webmail is a World Wide Web interface that allows users to read and write E-mail using a Web browser. ... An open mail relay is an SMTP (email) server configured in such a way that it allows anyone on the Internet to relay (i. ... A typical spam advertisement Spam by e-mail is one type of spamming that involves sending identical or nearly identical messages to thousands (or millions) of recipients. ...


Message format

The format of Internet e-mail messages is defined in RFC 2822. Prior to the introduction of RFC 2822 the format was described by RFC 822.


Internet e-mail messages consist of two major components:

  • Headers - Message summary, sender, receiver, and other information about the e-mail
  • Body - The message itself, usually containing a signature block at the end

The headers usually have at least four fields: A signature block (often abbreviated as signature, sig block, or just sig) is a block of text automatically appended at the bottom of an e-mail message, Usenet article, or forum post. ...

  1. From: The e-mail address of the sender of the message
  2. To: The e-mail address of the receiver of the message
  3. Subject: A brief summary of the contents of the message
  4. Date: The local time and date when the message was originally sent

Note however that the "To" field does not necessarily have the e-mail address of the recipient. The information supplied in the headers on the recipients computer is similar to that found on top of a conventional letter. The actual information such as who the message was addressed to is removed by the mail server after it assigns it to the correct user's mailbox. Also note that the from field does not have to be the real sender of the e-mail. It is very easy to fake the from line and let an e-mail seem to be from any mail address. It is possible to Digitally Sign an e-mail. This is much harder to fake. In cryptography, digital signatures are a method of authenticating digital information often treated, sometimes too closely, as analogous to a physical signature on paper. ...


Other common header fields include:

  1. Cc: Carbon copy (because typewriters use carbon paper to make copies of letters)
  2. Bcc: Blind carbon copy (the recipient of this copy will know who was in the To: field, but the recipients cannot see who is on the Bcc: list)
  3. Received: Tracking information generated by mail servers that have previously handled a message
  4. Content-Type: Information about how the message has to be displayed, usually a MIME type

Carbon Copy may be: A full name for Cc the cat A horse participated at the Cox Plate Carbon copy, a simple low technology copying technique This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Although still popular with a few writers and in less developed countries, the typewriter has largely been replaced by the word processor. ... Carbon paper (originally carbonic paper) is paper coated on one side with a layer with a loose ink or pigmented coating. ... A mime is the representation of action, character or mood using only gestures and movements rather than words, or the actor in such a performance, specifically a mimic or pantomimist. ...

Messages and mailboxes

Messages are exchanged between hosts using the Simple Mail Transfer Protocol with software like Sendmail. Users download their messages from servers usually with either the POP or IMAP protocols, yet in a large corporate environment users are likely to use some proprietary protocol such as Lotus Notes or Microsoft Exchange Server's. Simple Mail Transfer Protocol (SMTP) is the de facto standard for email transmission across the Internet. ... Sendmail is an open source mail transfer agent (MTA): a computer program for the routing and delivery of email. ... Post Office Protocol version 3 (POP3) is an application layer Internet standard protocol used to retrieve email from a remote server to a local client over a TCP/IP connection. ... The Internet Message Access Protocol (commonly known as IMAP, and previously called Interactive Mail Access Protocol) is an application layer Internet protocol used for accessing email on a remote server from a local client. ... A corporation (usually known in the United Kingdom and Ireland as a company) is a legal entity (distinct from a natural person) that often has similar rights in law to those of a Civil law systems may refer to corporations as moral persons; they may also go by the name... Something proprietary is something exclusively owned by someone, often with connotations that it is exclusive and cannot be used by other parties without negotiations. ... IBM Lotus Notes 6. ... Microsoft Exchange Server is a collaborative software server from Microsoft, positioned as a rival to the Lotus Notes / Domino server from IBM. The use of Microsoft Exchange is very widespread in large corporations using Microsoft infrastructure solutions. ...


Mails can be stored either on the client or on the server side. Standard formats for mailboxes include Maildir and mbox. Several prominent e-mail clients use their own, proprietary format, and require conversion software to transfer e-mail between them. In computing, a client is a system that accesses a (remote) service on another computer by some kind of network. ... This article is about computer servers. ... Maildir is a format for an e-mail spool that does not require file locking to maintain message integrity, because the messages are kept in separate files. ... Mbox is the name for several different things, including an electronic mail file format. ...


When a message cannot be delivered, the recipient MTA must send a bounce message back to the sender, indicating the problem. A bounce message, or Delivery Status Notification (DSN) message, is an electronic mail message sent by the mail system itself, to indicate that a message could not be delivered. ...


E-mail content encoding

E-mail is only defined to carry 7-bit ASCII messages. Although many e-mail transports are in fact "8-bit clean", this cannot be guaranteed. For this reason, e-mail has been extended by the MIME standard to allow the encoding of binary attachments including images, sounds and HTML attachments. There are 95 printable ASCII characters, numbered 32 to 126. ... A mime is the representation of action, character or mood using only gestures and movements rather than words, or the actor in such a performance, specifically a mimic or pantomimist. ... In computing, HyperText Markup Language (HTML) is a markup language designed for the creation of web pages and other information viewable in a browser. ...


Spamming and e-mail worms

The usefulness of e-mail is being threatened by two phenomena, spamming and e-mail worms. A typical spam advertisement Spam by e-mail is one type of spamming that involves sending identical or nearly identical messages to thousands (or millions) of recipients. ... A computer worm is a self-replicating computer program, similar to a computer virus. ...


Spamming is unsolicited commercial e-mail. Because of the very low cost of sending e-mail, spammers can send hundreds of millions of e-mail messages each day over an inexpensive Internet connection. Hundreds of active spammers sending this volume of mail results Information overload for many computer users who receive tens or even hundreds of junk e-mails each day. Information overload is a term that is usually used in conjunction with various forms of Computer-mediated communication such as Electronic mail. ...


E-mail worms use e-mail as a way of replicating themselves into vulnerable computers. Although the first e-mail worm (the Morris worm) affected early UNIX computers, this problem is today almost entirely confined to the Microsoft Windows operating system. The Morris worm was one of the first computer worms distributed via the Internet; it is considered the first worm virus and was certainly the first to gain significant mainstream media attention. ... Microsoft Windows is a range of commercial operating environments for personal computers. ...


The combination of spam and worm programs results in users receiving a constant drizzle of junk e-mail, which reduces the usefulness of e-mail as a practical tool.


A number of technology-based initiatives mitigate the impact of spam. In the United States, U.S. Congress has also passed a law, the Can Spam Act of 2003, attempting to regulate such e-mail. E-mail has become the subject of much abuse, in the form of both spamming and E-mail worm programs. ... The United States of America — also referred to as the United States, the U.S.A., the U.S., America, the States, or (archaically) Columbia—is a federal republic of 50 states located primarily in central North America (with the exception of two states: Alaska and Hawaii). ... Seal of the Congress. ... The CAN-SPAM Act of 2003, signed into law by President Bush on December 16, 2003, establishes the first national standards for the sending of commercial e-mail and requires the Federal Trade Commission (FTC) to enforce its provisions. ...


Privacy problems regarding e-mail

E-mail privacy, without some security precautions, can be compromised because

  • e-mail messages are generally not encrypted;
  • e-mail messages have to go through intermediate computers before reaching their destination, meaning it is relatively easy for others to intercept and read messages;
  • many Internet Service Providers (ISP) store copies of your email messages on their mail servers before they are delivered. The backups of these can remain up to several months on their server, even if you delete them in your mailbox.

There are cryptography applications that can serve as a remedy to the above, such as Virtual Private Networks, message encyption using PGP or the GNU Privacy Guard, encrypted communications with the e-mail servers using Transport Layer Security and Secure Sockets Layer, and/or encrypted authentication schemes such as Simple Authentication and Security Layer. Cryptography portal Cryptography (from Greek kryptós, hidden, and gráphein, to write) is, traditionally, the study of means of converting information from its normal, comprehensible form into an incomprehensible format, rendering it unreadable without secret knowledge — the art of encryption. ... A Virtual Private Network, or VPN, is a private communications network usually used within a company, or by several different companies or organizations, communicating over a public network. ... Pretty Good Privacy (PGP) is a computer program which provides cryptographic privacy and authentication. ... The GNU Privacy Guard (GnuPG or GPG) is a free software replacement for the PGP suite of cryptographic software, released under the GNU General Public License. ... Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. ... Simple Authentication and Security Layer (SASL) is a framework for authentication and authorization in Internet protocols. ...


See also

E-mail art (sometimes called Electronic Mail Art) is simply any kind of art sent by e-mail. ... Netiquette (neologism, a contraction of network etiquette) is a catch all term for the conventions of politeness recognised on Usenet, in mailing lists, and other electronic forums such as internet web boards. ... Information overload is a term that is usually used in conjunction with various forms of Computer-mediated communication such as Electronic mail. ... One of the more frequent jokes on the internet is to produce a fake or joke web counter. ... Internet slang - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... This article is about spam, the abuse of electronic communications media to send unsolicited bulk messages. ... E-mail has become the subject of much abuse, in the form of both spamming and E-mail worm programs. ... In computer security technology, a virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents (for a complete definition: see below). ... An email client (or mail user agent [MUA]) is a computer program that is used to read and send email. ... A mail transfer agent or MTA (also called a mail server, or a mail exchange server in the context of the Domain Name System) is a computer program or software agent which transfers electronic mail messages from one computer to another. ... Webmail is a World Wide Web interface that allows users to read and write E-mail using a Web browser. ... In computing, HyperText Markup Language (HTML) is a markup language designed for the creation of web pages and other information viewable in a browser. ... Branded email is a letterhead form of email. ... Electronic mailing lists are a special usage of email that allows for widespread distribution of information to many Internet users. ... A mailing list archive is a collection of past messages from one or more electronic mailing lists. ... An e-mail address identifies a location to which e-mail can be delivered. ... Internet e-mail functions through the use of a coordinated set of internet standards. ... Webmail is a World Wide Web interface that allows users to read and write E-mail using a Web browser. ... Hotmails login page MSN Hotmail layout Hotmail is one of the popular free webmail email services, which are accessible from anywhere on the planet via a standard web browser. ... The Yahoo! Mail login page. ... Google Mail is a free webmail service, currently in beta testing, created by Google. ... temporary hosting is a special kind of webmail. ... A Uniform Resource Identifier (URI), is an Internet protocol element consisting of a short string of characters that conform to a certain syntax. ... Vismon was the Bell Labs system which put authors faces on one of their internal email system. ...

Further reading

  • Katie Hafner, Matthew Lyon, Where Wizards Stay Up Late: The Origins of the Internet (Simon and Schuster, 1996) also covers the early history of e-mail
  • Abdullah, M. H. (1998). "Electronic discourse: Evolving conventions in online academic environments". Bloomington, IN: ERIC Clearinghouse on Reading, English, and Communication. [ED 422 593]
  • Abras, C. (2002) The principle of relevance and metamessages in online discourse: Electronic exchanges in a graduate course. Language, "Literacy and Culture Review" 1(2), 39-53.
  • Biesenbach-Lucas, S. & Wiesenforth, D. (2001). E-mail and word processing in the ESL classroom: How the medium affects the message. "Language Learning and Technology", 5 (1), 135-165. [EJ 621 506]
  • Danet, B. (2001). Cyberplay: Communicating online. Oxford: Berg Publishing.

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. The Free On-line Dictionary of Computing (FOLDOC) is an on-line, searchable encyclopedic dictionary of computing subjects. ... GFDL redirects here. ...

External links

  • The History of Electronic Mail (http://www.multicians.org/thvv/mail-history.html) is a personal memoir by the implementer of one of the first e-mail systems
  • Michael A. Padlipsky, And They Argued All Night... (http://www.mids.org/mn/1002/mike.html) is an alternative personal recollection of the origins of network e-mail
  • Is it Time to Start Encrypting Your E-mail? (http://www.windowsecurity.com/articles/Encrypting-Your-E-mail.html) - Discusses the pros and cons of E-mail encryption
  • E-Mail Counseling: Skills for Maximum Impact (http://www.ericdigests.org/2002-3/e-mail.htm)
  • The Impact of Electronic Communication on Writing (http://www.ericdigests.org/2004-1/impact.htm)
  • Email @ sourceforge.net (http://sourceforge.net/softwaremap/trove_list.php?form_cat=28)
  • Email Encoder: online tool to encode your website email address to prevent spam (http://www.email-encoder.com)
  • Guardian.co.uk  (http://www.guardian.co.uk/uk_news/story/0,3604,1465950,00.html) - 'Emails "pose threat to IQ"', Martin Wainwright, The Guardian (April 22, 2005)



Internet
Electronic mail - Usenet - World Wide Web - Instant messenger - File sharing

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