Electronic mail Guide, Meaning , Facts, Information and Description
E-mail, or email, is short for "electronic mail" (as opposed to conventional mail, in this context also called snail mail) and is a method of composing, sending, and receiving messages over electronic communication systems. Most e-mail systems today use the Internet, and e-mail is one of the most popular uses of 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.
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 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 creation, 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 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.
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-reachable location to the addressee, so called because each hop is signified by a "bang sign", i.e. 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.
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.
The diagram above shows a stereotypical sequence of events that takes place when Alice sends an e-mail to Bob.
Internet e-mail messages consist of two major components:
Other common header fields include:
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.
When a message cannot be delivered, the recipient MTA must send a bounce message back to the sender, indicating the problem.
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 in many computer users receiving tens or even hundreds of junk e-mails each 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 early 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. In the United States, Congress has also passed a law, the Can Spam Act of 2003, to regulate such e-mail.
This is an Article on Electronic mail. Page Contains Information, Facts Details or Explanation Guide About Electronic mail 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.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.Modern Internet e-mail
How e-mail works
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:
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.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.
The headers usually have at least four fields:
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.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.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 attachmentss including images, sounds and HTML attachments.Spamming and e-mail worms
The usefulness of e-mail is being threatened by two phenomena, spamming and e-mail worms. See also
Further reading
References
External links