Electronic mail, often abbreviated to e-mail, email, or simply mail, is a store-and-forward method of composing, sending, receiving and storing messages over electronic communication systems. Theterm "e-mail" (as a noun or verb) applies both to the Internet e-mail system based on the Simple Mail Transfer Protocol (SMTP) and to X.400 systems, and to intranet systems allowing users within oneorganization to e-mail each other. Intranets may use the Internet protocols or X.400 protocols for internal e-mail service supporting workgroup collaboration. E-mail is often used to deliver bulkunsolicited messages, or "spam", but filter programs exist which can automatically delete some or most of these, depending on the situation.
Spelling
The spellings e-mail and email are both common. Several prominent journalistic and technical style guides recommend e-mail, and the spelling email is also recognized in many dictionaries. In theoriginal RFC definitions for the Internet's electronic mail system, neither spelling is used; the service is referred to as mail, and a single piece of electronic mail is called a message. Some laterRFCs use email.
Origin
E-mail predates the inception of the Internet, and was in fact a crucial tool in creating the Internet. MIT first demonstrated the Compatible Time-Sharing System (CTSS) in 1961. It allowedmultiple users to log into the IBM 7094 from remote dial-up terminals, and to store files online on disk. This new ability encouraged users to share information in new ways.
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 wereSDC's Q32 and MIT's CTSS. E-mail was quickly extended to become network e-mail, allowing users to pass messages between different computers by at least 1966 (it is possible the SAGE system hadsomething similar some time before).
The ARPANET computer network made a large contribution to the development of e-mail. There is one report that indicates experimental inter-system e-mail transfers on it shortly after its creationin 1969. Ray Tomlinson initiated the use of the @ sign to separate the names of the user and their machine in 1971. The ARPANET significantly increased the popularity of e-mail, and it became thekiller app of the ARPANET.
Format
The format of Internet e-mail messages is defined in RFC 2822 and a series of RFCs, RFC 2045 through RFC 2049, collectively called Multipurpose Internet Mail Extensions (MIME). Although as of July13, 2005 RFC 2822 is technically a proposed IETF standard and the MIME RFCs are draft IETF standards, these documents are the de facto standards for the format of Internet e-mail.
Prior to the introduction of RFC 2822 in 2001 the format described by RFC 822 was the de facto standard for Internet e-mail for nearly two decades; it is still the official IETF standard. The IETFreserved the numbers 2821 and 2822 for the updated versions of RFC 821 (SMTP) and RFC 822, honoring the extreme importance of these two RFCs. RFC 822 was published in 1982 and based on the earlierRFC 733
Internet e-mail messages consist of two major sections: Header — Structured into fields such as summary, sender, receiver, and other information about the e-mail Body — The messageitself as unstructured text; sometimes containing a signature block at the end. The header is separated from the body by a blank line.
Header
The message header consists of fields, usually including at least the following:
From: The e-mail address, and optionally the name of the sender.
To: The e-mail address[es], and optionally name[s] of the message's recipient[s]
Subject: A brief summary of the contents of the message
Date: The local time and date when the message was written
Each header field has a name and a value. RFC 2822 specifies the precise syntax. Informally, the field name starts in the first character of a line, followed by a ":", followed by the value whichis continued on non-null subsequent lines that have a space or tab as their first character. Field names and values are restricted to 7-bit ASCII characters. Non-ASCII values may be represented usingMIME encoded words.
Note that the "To" field in the header is not necessarily related to the addresses to which the message is delivered. The actual delivery list is supplied in the SMTP protocol, not extracted fromthe header content. The "To" field is similar to the greeting at the top of a conventional letter which is delivered according to the address on the outer envelope.
Also note that the "From" field does not have to be the real sender of the e-mail message. It is very easy to fake the "From" field and let a message seem to be from any mail address. It ispossible to digitally sign e-mail, which is much harder to fake.
Some Internet service providers do not relay e-mail claiming to come from a domain not hosted by them, but very few (if any) check to make sure that the person or even e-mail address named in the"From" field is the one associated with the connection. Some Internet service providers apply e-mail authentication systems to e-mail being sent through their MTA to allow other MTAs to detect forgedspam that might apparently appear to be from them.
Other common header fields include:
Cc: carbon copy
Bcc: Blind Carbon Copy
Received: Tracking information generated by mail servers that have previously handled a message.
Content-Type: Information about how the message has to be displayed, usually a MIME type.
Reply-To: Address that should be used to reply to the sender.
References: Message-ID of the message that this is a reply to, and the message-id of this message, etc.
In-Reply-To: Message-ID of the message that this is a reply to.
Many e-mail clients present "Bcc" (Blind carbon copy, recipients not visible in the "To" field) as a header field. Different protocols are used to deal with the "Bcc" field; at times the entirefield is removed, whereas other times the field remains but the addresses therein are removed. Addresses added as "Bcc" are only added to the SMTP delivery list, and do not get included in themessage data.
Body
Content encoding
E-mail was originally designed for 7-bit ASCII. Much e-mail software is 8-bit clean but must assume it will be communicating with 7-bit servers and mail readers. The MIME standard introducedcharacter set specifiers and two content transfer encodings to enable transmission of non-ASCII data: quoted printable for mostly 7 bit content with a few characters outside that range and base64 forarbitrary binary data. The 8BITMIME extension was introduced to allow transmission of mail without the need for these encodings but many mail transport agents still don't support it fully. Forinternational character sets, Unicode is growing in popularity.
Plain text and HTML
Both plain text and HTML are used to convey e-mail. While text is certain to be read by all users without problems, there is a perception that HTML-based e-mail has a higher aesthetic value.Advantages of HTML include the ability to include inline links and images, set apart previous messages in block quotes, wrap naturally on any display, use emphasis such as underlines and italics, andchange font styles.
HTML e-mail messages often include an automatically-generated plain text copy as well, for compatibility reasons. Disadvantages include the increased size of the email, privacy concerns about webbugs and that HTML email can be a vector for phishing attacks and the spread of malicious software.
Servers and client applications
Messages are exchanged between hosts using the Simple Mail Transfer Protocol with software programs called mail transport agents. Users can download their messages from servers with standardprotocols such as the POP or IMAP protocols, or, as is more likely in a large corporate environment, with a proprietary protocol specific to Lotus Notes or Microsoft Exchange Servers.
Mail can be stored either on the client, on the server side, or in both places. Standard formats for mailboxes include Maildir and mbox. Several prominent e-mail clients use their own proprietaryformat 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 theproblem.
Filename extensions
Most, but not all, e-mail clients save individual messages as separate files, or allow users to do so. Different applications save e-mail files with different filename extensions.
(.eml) - This is the default e-mail extension for Mozilla Thunderbird and Windows Mail.
The above is used by Microsoft Outlook Express as well.
(.emlx) - Used by Apple Mail.
(.msg) - Used by Microsoft Office Outlook.
Use
Flaming
Many observers bemoan the rise of flaming in written communications. Flaming occurs when one person sends an angry and/or antagonistic message. Flaming is assumed to be more common today becauseof the ease and impersonality of e-mail communications: confrontations in person or via telephone require direct interaction, where social norms encourage civility, whereas typing a message toanother person is an indirect interaction, so civility may be forgotten.
E-mail bankruptcy
Also known as "email fatigue", e-mail bankruptcy is when a user ignores a large number of e-mail messages after falling behind in reading and answering them. The reason for falling behind is oftendue to information overload and a general sense there is so much information that it is not possible to read it all. As a solution, people occasionally send a boilerplate message explaining that theemail inbox is being cleared out. Stanford University law professor Lawrence Lessig is credited with coining this term, but he may only have popularized it.
In business
E-mail was widely accepted by the business community as the first broad electronic communication medium and was the first ‘e-revolution’ in Business communication. E-mail is verysimple to understand and like postal mail, e-mail solves two basic problems of communication. LAN based email is also an emerging form of usage for business. It not only allows the business user todownload mail when offline, it also provides the small business user to have multiple users email ID's with just one email connection.
Pros
Much of the business world relies on communication between individuals who are physically distant from one another; organizing and participating in an in-person meeting can be time-consuming andexpensive. E-mail provides a near-instantaneous exchange of information at little cost. Teleconferencing bridges physical distance, but the logistics of gathering people together at the same timeremains.
For real time communication, participants generally have to be working on the same schedule. They need to be at the same place at the same time and spend the same amount of time on the sameinformation. E-mail allows each participant to decide when and how they will process the information.
Cons
Most business professionals today spend between 20% and 50% of their working time using e-mail:[21] reading, ordering, sorting, ‘re-contextualizing’ fragmented information and ofcourse writing e-mail. Use of e-mail is increasing, due to trends of globalization—distribution of organizational divisions, outsourcing, among others. E-mail can lead to some well-knownproblems:
Loss of Context: Information in context (as in a newspaper) is much easier and faster to understand than unsorted fragments. Communicating in context is faster and more efficient.
"Asocial Behaviorisms" Email can be an "easy out" for those with non-confrontational personalities, perverting the overall health of public discourse in a society that depends on authentic humaninteraction.
Spam: E-mail is a push-only medium: control of who receives information lies primarily with the sender. This can lead to an overflow of unwanted or irrelevant information.
Inconsistency: E-mail can duplicate information. This may be a problem when a team is collaboratively working on documents.
Despite these disadvantages, and despite the availability of other tools, e-mail-based communication is still the most widely used written medium in businesses.
Challenges
Information overload
A December 2007 New York Times blog post described E-mail as "a $650 Billion Drag on the Economy", and the New York Times reported in April 2008 that "E-MAIL has become the bane of somepeople’s professional lives" due to information overload, yet "none of [the current wave of high-profile Internet startups focused on email] really eliminates the problem of e-mail overloadbecause none helps us prepare replies". Technology investors reflect similar concerns.
Spamming and computer viruses
The usefulness of e-mail is being threatened by four phenomena: e-mail bombardment, spamming, phishing and e-mail worms. Spamming is unsolicited commercial e-mail. Because of the very low cost ofsending 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 ininformation overload for many computer users who receive voluminous unsolicited email each day.
E-mail worms use e-mail as a way of replicating themselves into vulnerable computers. Although the first e-mail worm affected UNIX computers, the problem is most common today on the more popularMicrosoft 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 anti-spam techniques 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. Australia alsohas very strict spam laws restricting the sending of spam from an Australian ISP, but its impact has been minimal since most spam comes from regimes that seem reluctant to regulate the sending ofspam.
Privacy concerns
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 beforereaching their destination, meaning it is relatively easy for others to intercept and read messages; many Internet Service Providers (ISP) store copies of your e-mail messages on their mail serversbefore they are delivered. The backups of these can remain up to several months on their server, even if you delete them in your mailbox; the Received: headers and other information in the e-mail canoften identify the sender, preventing anonymous communication.
There are cryptography applications that can serve as a remedy to one or more of the above. For example, Virtual Private Networks or the Tor anonymity network can be used to encrypt traffic fromthe user machine to a safer network while GPG, PGP or S/MIME can be used for end-to-end message encryption, and SMTP STARTTLS or SMTP over Transport Layer Security/Secure Sockets Layer can be used toencrypt communications for a single mail hop between the SMTP client and the SMTP server. Additionally, many mail user agents do not protect logins and passwords, making them easy to intercept by anattacker. Encrypted authentication schemes such as SASL prevent this. Finally, attached files share many of the same hazards as those found in peer-to-peer filesharing. Attached files may containtrojans or viruses.
Tracking of sent mail
The original SMTP mail service provides limited mechanisms for tracking a sent message, and none for verifying that it has been delivered or read. It requires that each mail server must eitherdeliver it onward or return a failure notice ("bounce message"), but both software bugs and system failures can cause messages to be lost. To remedy this, the IETF introduced Delivery StatusNotifications (delivery receipts) and Message Disposition Notifications (return receipts); however, these are not universally deployed in production.
US Government
Starting in 1977, the US Postal Service (USPS) recognized the electronic mail and electronic transactions posed a significant threat to First Class mail volumes and revenue. Therefore, the USPSinitiated an experimental e-mail service known as E-COM. Electronic messages would be transmitted to a post office, printed out, and delivered in hard copy form. In order to take advantage of theservice, an individual had to transmit at least 200 messages. The delivery time of the messages was the same as First Class mail and cost 26 cents. The service was said to be subsidized andapparently USPS lost substantial money on the experiment. Both the US Postal Commission and the Federal Communications Commission opposed E-COM. The FCC concluded that E-COM constituted commoncarriage under its jurisdiction and the USPS would have to file a tariff. Three years after initiating the service, USPS canceled E-COM and attempted to sell it off.
Early on in the history of the ARPANet, there were multiple e-mail clients which had various, and at times, incompatible formats. For example, in the system Multics, the "@" sign meant "kill line"and anything after the "@" sign would be ignored. The Department of Defense DARPA desired to have uniformity and interoperability for e-mail and therefore funded efforts to drive towards unifiedinteroperable standards. This led to David Crocker, John Vittal, Kenneth Pogran, and Austin Henderson publishing RFC 733, "Standard for the Format of ARPA Network Text Message" (Nov. 21, 1977), whichwas apparently not effective. In 1979, a meeting was held at BBN to resolve incompatibility issues. Jon Postel recounted the meeting in RFC 808, "Summary of Computer Mail Services Meeting Held at BBNon 10 January 1979" (March 1, 1982), which includes an appendix listing the varying e-mail systems at the time. This, in turn, lead to the release of David Crocker's RFC 822, "Standard for the Formatof ARPA Internet Text Messages" (Aug. 13, 1982).
The National Science Foundation took over operations of the ARPANet and Internet from the Department of Defense, and initiated NSFNet, a new backbone for the network. A part of the NSFNet AUP wasthat no commercial traffic would be permitted. In 1988, Vint Cerf arranged for an interconnection of MCI Mail with NSFNET on an experimental basis. The following year Compuserve e-mail interconnectedwith NSFNET. Within a few years the commercial traffic restriction was removed from NSFNETs AUP, and NSFNET was privatized. In the late 1990s, the Federal Trade Commission grew concerned with fraudtranspiring in e-mail, and initiated a series of procedures on SPAM, fraud, and phishing. In 2004, FTC jurisdiction over SPAM was codified into law in the form of the CAN SPAM Act. Several other USFederal Agencies have also exercised jurisdiction including the Department of Justice and the Secret Service.
