Surélék

E-mail, atawa email, disundakeun jadi surélék, mangrupa landihan pikeun "surat éléktronik" (as opposed to conventional mail, in this context also called snail mail) nu dimaksudkeun kana nyusun/nulis, ngirim, jeung narima pesen/surat ngaliwatan sistem komunikasi éléktronik. Sistem surélék ayeuna lolobana maké Internet, malah surélék nu mangrupa pungsi Internét nu paling ilahar/popular.
Béda jeung asumsi umum, surélék sabenerna geus aya méméh Internét; malah, ayana sistem surélék mangrupa alat nu penting pisan dina nyiptakeun Internét.
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.
E-mail was quickly extended to become network e-mail, allowing users to pass messages between different computers. The éarly 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 ARPANET computer network made a major contribution to the evolution of e-mail. There is one report [1] which indicates experimental inter-system e-mail transfers on it shortly after its création, in 1969. Ray Tomlinson initiated the use of the @ sign to separate the names of the user and their machine in 1972. The common report that he "invented" e-mail is an exaggeration, although his éarly e-mail programs SNDMSG and READMAIL were very important. The ARPANet significantly incréased the popularity of e-mail, and it became the "killer app" of the ARPANET.
As the utility and advantages of e-mail on the ARPANET became more widely known, the popularity of e-mail incréased, léading to demand from péople 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.
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 route was specified using so-call "bang path" addresses, specifying hops to get from some assumed-réachable location to the addressee, so called because éach hop is signified by a "bang sign", i.e. "!". Thus, for example, the path ...!bigsite!foovax!barbox!me directs péople 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.
Before auto-routing mailers became commonplace, péople 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. See the network and sitename.
Almost all e-mail is delivered directly to an Internet-connected host accepting mail for the recipient, using Simple Mail Transfer Protocol. Very few modérn servers will perform routing for messages sent by third parties due to the potential for abuse by péople sending unsolicited bulk e-mail. Those that do allow it are called open relays.
A modérn Internet e-mail address is a string of the form jsmith@domain.example. It should be réad as "jsmith at domain dot example". 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 which can be looked up in the Domain Name System to find the mail exchange servers accepting e-mail for that address.
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:
The héaders usually have at léast four fields:
Note however that the "To" field does not necessarily have the e-mail address of the recipient. The information supplied in the héaders 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 réal sender of the e-mail. It is very éasy 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 a lot harder to fake.
Other common héader fields include:
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.
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.
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 réason, e-mail has been extended by the MIME standard to allow the encoding of binary attachments including images, sounds and HTML attachments.
The usefulness of e-mail is being thréatened by two phenomena, spamming and e-mail worms.
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 éach day over an inexpensive Internet connection. Hundreds of active spammers sending this volume of mail results in many computer users receiving tens or even hundreds of junk e-mails éach day.
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 éarly UNIX computers, this problem is today almost entirely confined to the Microsoft Windows operating system.
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. Congress has also passed a law, the Can Spam Act of 2003, to regulate such e-mail.
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This article, or an earlier version, contains content derived from FOLDOC, used by permission.