Email

This article is about the communications medium. Forthe former manufacturing conglomerate, see Email Lim-ited.Inbox redirects here. For the Google product, seeGoogle Inbox.Electronicmail, most commonly referred to as email or

The at sign, a part of every SMTP email address.[1]

e-mail since c 1993,[2] is a method of exchanging digitalmessages from an author to one or more recipients. Mod-ern email operates across the Internet or other computernetworks. Some early email systems required the authorand the recipient to both be online at the same time, incommon with instant messaging. Todays email systemsare based on a store-and-forward model. Email serversaccept, forward, deliver, and store messages. Neither theusers nor their computers are required to be online si-multaneously; they need connect only briey, typicallyto a mail server, for as long as it takes to send or re-ceive messages. Historically, the term electronic mail wasused generically for any electronic document transmis-sion. For example, several writers in the early 1970s usedthe term to describe fax document transmission.[3][4] Asa result, it is dicult to nd the rst citation for the useof the term with the more specic meaning it has today.An Internet email message consists of three components,the message envelope, the message header, and the mes-sage body. The message header contains control informa-tion, including, minimally, an originators email addressand one or more recipient addresses. Usually descriptiveinformation is also added, such as a subject header eld

and a message submission date/time stamp.Originally a text-only (ASCII) communications medium,Internet email was extended to carry, e.g. text in othercharacter sets, multi-media content attachments, a pro-cess standardized in RFC 2045 through 2049. Collec-tively, these RFCs have come to be called MultipurposeInternet Mail Extensions (MIME). Subsequent RFCshave proposed standards for internationalized email ad-dresses using UTF-8.Electronic mail predates the inception of the Internet andwas in fact a crucial tool in creating it,[5] but the history ofmodern, global Internet email services reaches back to theearly ARPANET. Standards for encoding email messageswere proposed as early as 1973 (RFC 561). Conversionfrom ARPANET to the Internet in the early 1980s pro-duced the core of the current services. An email messagesent in the early 1970s looks quite similar to a basic textmessage sent on the Internet today.Email is an information and communications technology.It uses technology to communicate a digital message overthe Internet. Users use email dierently, based on howthey think about it. There are many software platformsavailable to send and receive. Popular email platforms in-clude Gmail, Hotmail, Yahoo! Mail, Outlook, and manyothers.[6]

Network-based email was initially exchanged on theARPANET in extensions to the File Transfer Protocol(FTP), but is now carried by the Simple Mail TransferProtocol (SMTP), rst published as Internet standard 10(RFC 821) in 1982. In the process of transporting emailmessages between systems, SMTP communicates deliv-ery parameters using a message envelope separate fromthe message (header and body) itself.

1 SpellingElectronic mail has several English spelling options thatoccasionally are the cause of vehement disagreement.

e-mail is the most common form. According toCorpus of Contemporary American English data,this is the form that appears most frequently inedited, published American English and British En-glish writing.[7]

email is the most common form used online,and is required by IETF Requests for Comments

1

2 2 ORIGIN

and working groups[8] and increasingly by styleguides.[9][10][11] This spelling also appears in mostdictionaries.[12][13][14][15][16][17][18]

mail was the form used in the original RFC. Theservice is referred to as mail, and a single piece ofelectronic mail is called a message.[19][20][21]

EMail is a traditional form that has been used inRFCs for the Authors Address[20][21] and is ex-pressly required for historical reasons.[22]

E-mail is sometimes used, capitalizing the initial Eas in similar abbreviations like E-piano, E-guitar, A-bomb, and H-bomb.[23]

2 OriginThe AUTODIN network, rst operational in 1962, pro-vided a message service between 1,350 terminals, han-dling 30 million messages per month, with an averagemessage length of approximately 3,000 characters. Au-todin was supported by 18 large computerized switches,and was connected to the United States General Ser-vices Administration Advanced Record System, whichprovided similar services to roughly 2,500 terminals.[24]

2.1 Host-based mail systemsWith the introduction of MIT's Compatible Time-Sharing System (CTSS) in 1961[25] multiple users wereable to log into a central system[26] from remote dial-up terminals, and to store and share les on the centraldisk.[27] Informal methods of using this to pass messageswere developed and expanded :

1965 MIT's CTSS MAIL.[28]

Developers of other early systems developed similaremail applications:

1962 1440/1460 Administrative Terminal Sys-tem[29]

1968 ATS/360[30][31]

1971 SNDMSG, a local inter-user mail programincorporating the experimental le transfer pro-gram, CPYNET, allowed the rst networked elec-tronic mail[32]

1972 Unix mail program[33][34]

1972 APL Mailbox by Larry Breed[35][36]

1974 The PLATO IV Notes on-line messageboard system was generalized to oer 'personalnotes in August 1974.[24][37]

1978 Mail client written by Kurt Shoens for Unixand distributed with the Second Berkeley SoftwareDistribution included support for aliases and distri-bution lists, forwarding, formatting messages, andaccessing dierent mailboxes.[38] It used the Unixmail client to send messages between system users.The concept was extended to communicate remotelyover the Berkley Network.[39]

1979 EMAIL written by V.A. Shiva Ayyadurai toemulate the interoce mail system of the Universityof Medicine and Dentistry of New Jersey[40][41]

1979 MH Message Handling System developedat RAND provided several tools for managing elec-tronic mail on Unix.[42]

1981 PROFS by IBM[43][44]

1982 ALL-IN-1[45] by Digital Equipment Corpo-ration

These original messaging systems had widely dierentfeatures and ran on systems that were incompatible witheach other. Most of them only allowed communicationbetween users logged into the same host or mainframe,although there might be hundreds or thousands of userswithin an organization.

2.2 LAN email systemsIn the early 1980s, networked personal computers onLANs became increasingly important. Server-based sys-tems similar to the earlier mainframe systems were de-veloped. Again, these systems initially allowed commu-nication only between users logged into the same serverinfrastructure. Examples include:

cc:Mail Lantastic WordPerfect Oce Microsoft Mail Banyan VINES Lotus Notes

Eventually these systems too could link dierent orga-nizations as long as they ran the same email system andproprietary protocol.[46]

2.3 Email networksTo facilitate electronic mail exchange between remotesites and with other organizations, telecommunicationlinks, such as dialup modems or leased lines, providedmeans to transport email globally, creating local andglobal networks.

2.5 From SNDMSG to MSG 3

In 1971 the rst ARPANET email was sent,[47] andthrough RFC 561, RFC 680, RFC 724, and nally1977s RFC 733, became a standardized workingsystem.

PLATO IV was networked to individual terminalsover leased data lines prior to the implementation ofpersonal notes in 1974.[37]

Unix mail was networked by 1978s uucp,[48] whichwas also used for USENET newsgroup postings

BerkNet, the Berkeley Network, written by EricSchmidt in 1978 and included rst in the SecondBerkeley Software Distribution provided support forsending and receiving messages over serial commu-nication links. The Unix mail tool was extended tosend messages using BerkNet.[39]

The delivermail tool written by Eric Allman in 1979and 1980 (and shipped in 4BSD) provided supportfor routing mail over dierent networks includingArpanet, UUCP, and BerkNet. (It also providedsupport for mail user aliases.)[49]

The mail client included in 4BSD (1980) was ex-tended to provide interoperability between a varietyof mail systems.[50]

BITNET (1981) provided electronic mail servicesfor educational institutions. It was based on the IBMVNET email system.[51]

In 1984, IBM PCs running DOS could link withFidoNet for email and shared bulletin board post-ing.

2.4 Attempts at interoperabilityEarly interoperability among independent systems in-cluded:

ARPANET, a forerunner of the Internet, denedprotocols for dissimilar computers to exchangeemail.

uucp implementations for Unix systems, and laterfor other operating systems, that only had dial-upcommunications available.

CSNET, which initially used the UUCP protocolsvia dial-up to provide networking andmail-relay ser-vices for non-ARPANET hosts.

Novell developed the Message Handling System(MHS) protocol[52][53][54] but abandoned it afterpurchasing the non-MHS WordPerfect Oce (re-named Groupwise)

The Coloured Book protocols on UK academic net-works until 1992

X.400 in the 1980s and early 1990s was promotedbymajor vendors, andmandated for government useunder GOSIP, but abandoned by all but a few in fa-vor of Internet SMTP by the mid-1990s.

2.5 From SNDMSG to MSG

In the early 1970s, Ray Tomlinson updated an exist-ing utility called SNDMSG so that it could copy mes-sages (as les) over the network. Lawrence Roberts Theproject manager for the ARPANET development, tookthe idea of READMAIL, which dumped all recentmes-sages onto the users terminal, and wrote a programmefor TENEX in TECO macros called RD, which permit-ted access to individual messages.[55] Barry Wessler thenupdated RD and called it NRD.[56]

Marty Yonke rewrote NRD to include reading, accessto SNDMSG for sending, and a help system, and calledthe utilityWRD, which was later known as BANANARD.John Vittal then updated this version to include three im-portant commands: Move (combined save/delete com-mand), Answer (determined to whom a reply should besent) and Forward (sent an email to a person who wasnot already a recipient). The system was called MSG.With inclusion of these features, MSG is considered tobe the rst integrated modern email programme, fromwhich many other applications have descended.[55]

2.6 ARPANET mail

Experimental email transfers between separate computersystems began shortly after the creation of theARPANETin 1969.[28] Ray Tomlinson is generally credited as havingsent the rst email across a network, initiating the useof the "@" sign to separate the names of the user andthe users machine in 1971, when he sent a message fromone Digital Equipment Corporation DEC-10 computer toanother DEC-10. The two machines were placed next toeach other.[32][57] Tomlinsons work was quickly adoptedacross the ARPANET, which signicantly increased thepopularity of email. For many years, email was the killerapp of the ARPANET and then the Internet.As the inuence of the ARPANET and later the Inter-net grew, gateways were developed to pass mail betweenit and other networks such as JANET, BITNET, X.400,FidoNet, and UUCP. This often involved addresses suchas:hubhost!middlehost!edgehost!user@uucpgateway.somedomain.example.comDespite the complex format of some such addresses, (inthis case an Internet email address to route mail to a userwith a "bang path" address at a UUCP host), they didlead to the universal connectivity that is the key featureof modern email.

4 4 MESSAGE FORMAT

3 Operation overviewThe diagram to the right shows a typical sequence ofevents[58] that takes place when Alice composes a mes-sage using her mail user agent (MUA). She enters theemail address of her correspondent, and hits the sendbutton.

1. Her MUA formats the message in email formatand uses the Submission Protocol (a prole of theSimple Mail Transfer Protocol (SMTP), see RFC6409) to send the message to the local mail submis-sion agent (MSA), in this case smtp.a.org, run byAlices internet service provider (ISP).

2. The MSA looks at the destination address pro-vided in the SMTP protocol (not from the mes-sage header), in this case bob@b.org. An Inter-net email address is a string of the form local-part@exampledomain. The part before the @ signis the local part of the address, often the usernameof the recipient, and the part after the @ sign isa domain name or a fully qualied domain name.The MSA resolves a domain name to determine thefully qualied domain name of the mail server in theDomain Name System (DNS).

3. The DNS server for the b.org domain, ns.b.org,responds with any MX records listing the mailexchange servers for that domain, in this casemx.b.org, a message transfer agent (MTA) serverrun by Bobs ISP.

4. smtp.a.org sends the message to mx.b.org usingSMTP.

This server may need to forward the message to otherMTAs before the message reaches the nal message de-livery agent (MDA).

1. The MDA delivers it to the mailbox of the user bob.

2. Bob presses the getmail button in hisMUA,whichpicks up the message using either the Post OceProtocol (POP3) or the Internet Message AccessProtocol (IMAP).

That sequence of events applies to the majority of emailusers. However, there are many alternative possibilitiesand complications to the email system:

Alice or Bob may use a client connected to a cor-porate email system, such as IBM Lotus Notes orMicrosoft Exchange. These systems often have theirown internal email format and their clients typicallycommunicate with the email server using a vendor-specic, proprietary protocol. The server sends orreceives email via the Internet through the products

Internet mail gateway which also does any necessaryreformatting. If Alice and Bob work for the samecompany, the entire transaction may happen com-pletely within a single corporate email system.

Alice may not have a MUA on her computer but in-stead may connect to a webmail service.

Alices computer may run its ownMTA, so avoidingthe transfer at step 1.

Bob may pick up his email in many ways, for exam-ple logging into mx.b.org and reading it directly, orby using a webmail service.

Domains usually have several mail exchange serversso that they can continue to accept mail when themain mail exchange server is not available.

Email messages are not secure if email encryptionis not used correctly.

ManyMTAs used to accept messages for any recipient onthe Internet and do their best to deliver them. SuchMTAsare called openmail relays. This was very important in theearly days of the Internet when network connections wereunreliable. If an MTA couldn't reach the destination, itcould at least deliver it to a relay closer to the destination.The relay stood a better chance of delivering the messageat a later time. However, this mechanism proved to beexploitable by people sending unsolicited bulk email andas a consequence very few modern MTAs are open mailrelays, and manyMTAs don't accept messages from openmail relays because such messages are very likely to bespam.

4 Message formatThe Internet email message format is now dened byRFC 5322, with multi-media content attachments beingdened in RFC 2045 through RFC 2049, collectivelycalled Multipurpose Internet Mail Extensions or MIME.RFC 5322 replaced the earlier RFC 2822 in 2008, andin turn RFC 2822 in 2001 replaced RFC 822 whichhad been the standard for Internet email for nearly 20years. Published in 1982, RFC 822 was based on theearlier RFC 733 for the ARPANET.[59]

Internet email messages consist of two major sections:

Header Structured into elds such as From, To,CC, Subject, Date, and other information about theemail.

Body The basic content, as unstructured text;sometimes containing a signature block at the end.This is exactly the same as the body of a regular let-ter.

The header is separated from the body by a blank line.

4.1 Message header 5

4.1 Message headerEach message has exactly one header, which is structuredinto elds. Each eld has a name and a value. RFC 5322species the precise syntax.Informally, each line of text in the header that begins witha printable character begins a separate eld. The eldname starts in the rst character of the line and ends be-fore the separator character ":". The separator is thenfollowed by the eld value (the body of the eld). Thevalue is continued onto subsequent lines if those lineshave a space or tab as their rst character. Field namesand values are restricted to 7-bit ASCII characters. Non-ASCII values may be represented using MIME encodedwords.

4.1.1 Header elds

Email header elds can be multi-line, and each lineshould be at most 78 characters long and in no eventmore than 998 characters long.[60] Header elds denedby RFC 5322 can only contain US-ASCII characters;for encoding characters in other sets, a syntax speci-ed in RFC 2047 can be used.[61] Recently the IETFEAI working group has dened some standards trackextensions,[62][63] replacing previous experimental exten-sions, to allow UTF-8 encoded Unicode characters to beused within the header. In particular, this allows emailaddresses to use non-ASCII characters. Such charactersmust only be used by servers that support these exten-sions.The message header must include at least the followingelds:[64]

From: The email address, and optionally the nameof the author(s). In many email clients not change-able except through changing account settings.

Date: The local time and date when the message waswritten. Like the From: eld, many email clients llthis in automatically when sending. The recipientsclient may then display the time in the format andtime zone local to him/her.

The message header should include at least the followingelds:[65]

Message-ID: Also an automatically generated eld;used to prevent multiple delivery and for referencein In-Reply-To: (see below).

In-Reply-To: Message-ID of the message that this isa reply to. Used to link related messages together.This eld only applies for reply messages.

RFC 3864 describes registration procedures for messageheader elds at the IANA; it provides for permanent and

provisional message header eld names, including alsoelds dened for MIME, netnews, and http, and refer-encing relevant RFCs. Common header elds for emailinclude:[66]

To: The email address(es), and optionally name(s)of the messages recipient(s). Indicates primary re-cipients (multiple allowed), for secondary recipientssee Cc: and Bcc: below.

Subject: A brief summary of the topic of the mes-sage. Certain abbreviations are commonly used inthe subject, including RE:" and FW:".

Bcc: Blind carbon copy; addresses added to theSMTP delivery list but not (usually) listed in themessage data, remaining invisible to other recipi-ents.

Cc: Carbon copy; Many email clients will markemail in ones inbox dierently depending onwhether they are in the To: or Cc: list.

Content-Type: Information about how the messageis to be displayed, usually a MIME type.

Precedence: commonly with values bulk, junk,or list"; used to indicate that automated vacationor out of oce responses should not be returnedfor this mail, e.g. to prevent vacation notices frombeing sent to all other subscribers of a mailing list.Sendmail uses this header to aect prioritization ofqueued email, with Precedence: special-deliverymessages delivered sooner. With modern high-bandwidth networks delivery priority is less of an is-sue than it once was. Microsoft Exchange respects ane-grained automatic response suppression mech-anism, the X-Auto-Response-Suppress header.[67]

References: Message-ID of the message that this isa reply to, and the message-id of the message theprevious reply was a reply to, etc.

Reply-To: Address that should be used to reply tothe message.

Sender: Address of the actual sender acting on be-half of the author listed in the From: eld (secretary,list manager, etc.).

Archived-At: A direct link to the archived form ofan individual email message.

Note that the To: eld is not necessarily related to theaddresses to which the message is delivered. The actualdelivery list is supplied separately to the transport proto-col, SMTP, which may or may not originally have beenextracted from the header content. The To:" eld is sim-ilar to the addressing at the top of a conventional letterwhich is delivered according to the address on the outerenvelope. In the same way, the From:" eld does not

6 5 SERVERS AND CLIENT APPLICATIONS

have to be the real sender of the email message. Somemail servers apply email authentication systems to mes-sages being relayed. Data pertaining to servers activity isalso part of the header, as dened below.SMTP denes the trace information of a message, whichis also saved in the header using the following twoelds:[68]

Received: when an SMTP server accepts a messageit inserts this trace record at the top of the header(last to rst).

Return-Path: when the delivery SMTP server makesthe nal delivery of a message, it inserts this eld atthe top of the header.

Other header elds that are added on top of the headerby the receiving server may be called trace elds, in abroader sense.[69]

Authentication-Results: when a server carries out au-thentication checks, it can save the results in thiseld for consumption by downstream agents.[70]

Received-SPF: stores results of SPF checks in moredetail than Authentication-Results.[71]

Auto-Submitted: is used to mark automatically gen-erated messages.[72]

VBR-Info: claims VBR whitelisting[73]

4.2 Message body4.2.1 Content encoding

Email was originally designed for 7-bit ASCII.[74] Mostemail software is 8-bit clean but must assume it will com-municate with 7-bit servers and mail readers. The MIMEstandard introduced character set speciers and two con-tent transfer encodings to enable transmission of non-ASCII data: quoted printable formostly 7 bit content witha few characters outside that range and base64 for arbi-trary binary data. The 8BITMIME and BINARY exten-sions were introduced to allow transmission of mail with-out the need for these encodings, but many mail transportagents still do not support them fully. In some countries,several encoding schemes coexist; as the result, by de-fault, the message in a non-Latin alphabet language ap-pears in non-readable form (the only exception is coinci-dence, when the sender and receiver use the same encod-ing scheme). Therefore, for international character sets,Unicode is growing in popularity.

4.2.2 Plain text and HTML

Most modern graphic email clients allow the use of eitherplain text or HTML for the message body at the option of

the user. HTML email messages often include an auto-matically generated plain text copy as well, for compati-bility reasons.Advantages of HTML include the ability to include in-line links and images, set apart previous messages inblock quotes, wrap naturally on any display, use emphasissuch as underlines and italics, and change font styles. Dis-advantages include the increased size of the email, pri-vacy concerns about web bugs, abuse of HTML email asa vector for phishing attacks and the spread of malicioussoftware.[75]

Some web based Mailing lists recommend that all postsbe made in plain-text, with 72 or 80 characters perline[76][77] for all the above reasons, but also because theyhave a signicant number of readers using text-basedemail clients such as Mutt.Some Microsoft email clients allow rich formatting us-ing RTF, but unless the recipient is guaranteed to have acompatible email client this should be avoided.[78]

In order to ensure that HTML sent in an email is renderedproperly by the recipients client software, an additionalheader must be specied when sending: Content-type:text/html. Most email programs send this header auto-matically.

5 Servers and client applications

The interface of an email client, Thunderbird.

Messages are exchanged between hosts using the SimpleMail Transfer Protocol with software programs calledmail transfer agents (MTAs); and delivered to a mail storeby programs called mail delivery agents (MDAs, alsosometimes called local delivery agents, LDAs). Userscan retrieve their messages from servers using standardprotocols such as POP or IMAP, or, as is more likely in alarge corporate environment, with a proprietary protocolspecic to Novell Groupwise, Lotus Notes or MicrosoftExchange Servers. Webmail interfaces allow users to ac-cess their mail with any standard web browser, from anycomputer, rather than relying on an email client. Pro-grams used by users for retrieving, reading, andmanaging

7email are called mail user agents (MUAs).Mail can be stored on the client, on the server side, orin both places. Standard formats for mailboxes includeMaildir and mbox. Several prominent email clients usetheir own proprietary format and require conversion soft-ware to transfer email between them. Server-side stor-age is often in a proprietary format but since access isthrough a standard protocol such as IMAP, moving emailfrom one server to another can be done with any MUAsupporting the protocol.Accepting a message obliges anMTA to deliver it,[79] andwhen amessage cannot be delivered, thatMTAmust senda bounce message back to the sender, indicating the prob-lem.

5.1 Filename extensionsUpon reception of email messages, email client applica-tions save messages in operating system les in the lesystem. Some clients save individual messages as sepa-rate les, while others use various database formats, oftenproprietary, for collective storage. A historical standardof storage is the mbox format. The specic format usedis often indicated by special lename extensions:

eml Used bymany email clients including Novell Group-Wise, Microsoft Outlook Express, Lotus notes,Windows Mail, Mozilla Thunderbird, and Postbox.The les are plain text in MIME format, containingthe email header as well as the message contents andattachments in one or more of several formats.

emlx Used by Apple Mail.

msg Used by Microsoft Oce Outlook and OceLogicGroupware.

mbx Used by Opera Mail, KMail, and Apple Mail basedon the mbox format.

Some applications (like Apple Mail) leave attachmentsencoded in messages for searching while also saving sep-arate copies of the attachments. Others separate attach-ments from messages and save them in a specic direc-tory.Mobile devices, such as cell phones and tablet comput-ers, commonly have the ability to receive email. Sinceusers may always have their mobile device with them,users may access email signicantly faster on these de-vices than through other methods, such as desktop com-puters or laptops.

5.2 URI scheme mailtoMain article: mailto

The URI scheme, as registered with the IANA, denesthe mailto: scheme for SMTP email addresses. Thoughits use is not strictly dened, URLs of this form are in-tended to be used to open the new message window ofthe users mail client when the URL is activated, with theaddress as dened by the URL in the To: eld.[80]

6 Types

6.1 Web-based email (webmail)Main article: Webmail

Many email providers have a web-based email client (e.g.AOLMail, Gmail, Outlook.com and Yahoo! Mail). Thisallows users to log into the email account by using anycompatible web browser to send and receive their email.Mail is typically not downloaded to the client, so can't beread without a current Internet connection.

6.2 POP3 email servicesMain article: POP3

POP3 is the acronym for Post Oce Protocol 3. In aPOP3 email account, email messages are downloadedto the client device (i.e. a computer) and then they aredeleted from the mail server unless specic instructionto save has been given . It is dicult to save and viewmessages on multiple devices. Also, the messages sentfrom the computer/one device are not copied to the SentItems folder on the (other) devices. The messages aredeleted from the server to make room for more incomingmessages. POP supports simple download-and-delete re-quirements for access to remote mailboxes (termed mail-drop in the POP RFCs).[81] Although most POP clientshave an option to leave messages on the server afterdownloading a copy of them, most email clients usingPOP3 simply connect, retrieve all messages, store themon the client device as new messages, delete them fromthe server, and then disconnect.

6.3 IMAP email serversMain article: IMAP

IMAP refers to Internet Message Access Protocol. Withan IMAP account, a users account has access to mailfolders on the mail server and can use any compatibledevice to read and reply to messages, as long as sucha device can access the server. Small portable deviceslike smartphones are increasingly used to check emailwhile travelling, and to make brief replies, larger deviceswith better keyboard access being used to reply at greater

8 7 USE

length. IMAP shows the headers of messages, the senderand the subject and the device needs to request to down-load specic messages. Usually mail is left in folders inthe mail server.

6.4 MAPI email serversMain article: MAPI

Messaging Application Programming Interface (MAPI)is a messaging architecture and a Component ObjectModel based API for Microsoft Windows.

7 Use

7.1 FlamingFlaming occurs when a person sends a message with an-gry or antagonistic content. The term is derived fromthe use of the word Incendiary to describe particularlyheated email discussions. Flaming is assumed to be morecommon today because of the ease and impersonality ofemail communications: confrontations in person or viatelephone require direct interaction, where social normsencourage civility, whereas typing a message to anotherperson is an indirect interaction, so civility may be for-gotten.

7.2 Email bankruptcyMain article: Email bankruptcy

Also known as email fatigue, email bankruptcy is whena user ignores a large number of email messages afterfalling behind in reading and answering them. The rea-son for falling behind is often due to information overloadand a general sense there is so much information that it isnot possible to read it all. As a solution, people occasion-ally send a boilerplate message explaining that the emailinbox is being cleared out. Harvard University law pro-fessor Lawrence Lessig is credited with coining this term,but he may only have popularized it.[82]

7.3 In businessEmail was widely accepted by the business community asthe rst broad electronic communicationmedium andwasthe rst 'e-revolution' in business communication. Emailis very simple to understand and like postal mail, emailsolves two basic problems of communication: logisticsand synchronization (see below).LAN based email is also an emerging form of usage forbusiness. It not only allows the business user to down-

load mail when oine, it also allows the small businessuser to have multiple users email IDs with just one emailconnection.

7.3.1 Pros

The problem of logistics: Much of the business worldrelies on communications between people who arenot physically in the same building, area, or evencountry; setting up and attending an in-person meet-ing, telephone call, or conference call can be incon-venient, time-consuming, and costly. Email pro-vides a method of exchanging information betweentwo or more people with no set-up costs and that isgenerally far less expensive than a physical meetingor phone call.

The problem of synchronisation: With real timecommunication by meetings or phone calls, partici-pantsmust work on the same schedule, and each par-ticipant must spend the same amount of time in themeeting or call. Email allows asynchrony: each par-ticipant may control their schedule independently.

7.3.2 Cons

Most business workers today spend from one to two hoursof their working day using email: reading, ordering,sorting, 're-contextualizing' fragmented information, andwriting email.[83] The use of email is increasing world-wide:

Information overload: Email is a push technology the sender controls who receives the information.Convenient availability of mailing lists and use ofcopy all can lead to people receiving unwanted orirrelevant information of no use to them.

Inconsistency: Email can duplicate information.This can be a problem when a large team is workingon documents and information while not in constantcontact with the other members of their team.

Despite these disadvantages, email has become the mostwidely used medium of communication within the busi-ness world. A 2010 study on workplace communica-tion by Paytronics found 83% of U.S. knowledge workersfelt email was critical to their success and productivity atwork.[84]

7.3.3 Research on email marketing

Marketing research suggests that opt-in email marketingcan be viewed as useful by consumers if it contains in-formation such as special sales oerings and new productinformation. Oering interesting hyperlinks or generic

9information on consumer trends is less useful.[85] This re-search by Martin et al. (2003) also shows that if con-sumers nd email marketing useful, they are likely to visita store, thereby overcoming limitations of Internet mar-keting such as not being able to touch or try on a product.

7.4 MobileEmail has become widely used on smart phones. Mo-bile apps for email increase accessibility to the medium.While before users could only access email on comput-ers, it is now possible for users to check their email outof the home and out of the library while on the go. Alertscan also be sent to the phone to notify them immedi-ately of new messages. This has given email the ability tobe used for more frequent communication between usersand allowed them to check their email and write messagesthroughout the day.It was found that US adults check their email morethan they browse the web or check their Facebook ac-counts, making email the most popular activity for usersto do on their smart phones. 78% of the respondents inthe study revealed that they check their email on theirphone.[86] It was also found that 30% of consumers useonly their smartphone to check their email, and 91%werelikely to check their email at least once per day on theirsmartphone. However, the percentage of consumers us-ing email on smartphone ranges and diers dramaticallyacross dierent countries. For example, in comparisonto 75% of those consumers in the US who used it, only17% in India did.[87]

8 SecurityData condentiality, authentication, integrity, non-repudiation, access control, and availability are the mostimportant security services that should be considered insecure applications and systems, but they are not pro-vided in traditional email protocols. Email is vulnerableto both passive and active attacks. Passive threats includerelease of message contents, and trac analysis whileactive threats include modication of message contents,masquerade, replay, and denial-of-service (DoS). All thementioned threats are applicable to the traditional emailprotocols:

Disclosure of Information Trac analysis Modication of messages Masquerade Replay of previous messages Spoong

Denial of Service [88]

There are also concerns regarding the email privacy.

9 Problems

9.1 Attachment size limitationMain article: Email attachment

Email messages may have one or more attachments, i.e.MIME parts intended to provide copies of les. Attach-ments serve the purpose of delivering binary or text lesof unspecied size. In principle there is no technical in-trinsic restriction in the InternetMessage Format, SMTPprotocol or MIME limiting the size or number of attach-ments. In practice, however, email service providers im-plement various limitations on the permissible size of lesor the size of an entire message.Furthermore, due to technical reasons, often a small at-tachment can increase in size when sent,[89] which can beconfusing to senders when trying to assess whether theycan or cannot send a le by email, and this can result intheir message being rejected.As larger and larger le sizes are being created and traded,many users are either forced to upload and download theirles using an FTP server, or more popularly, use onlinele sharing facilities or services, usually over web-friendlyHTTP, in order to send and receive them.

9.2 Information overloadA December 2007 New York Times blog post describedinformation overload as a $650 Billion Drag on theEconomy,[90] and the New York Times reported inApril 2008 that E-MAIL has become the bane of somepeoples professional lives due to information overload,yet none of the current wave of high-prole Internetstart-ups focused on email really eliminates the prob-lem of email overload because none helps us preparereplies.[91] GigaOm posted a similar article in Septem-ber 2010, highlighting research that found 57% of knowl-edge workers were overwhelmed by the volume of emailthey received.[84] Technology investors reect similarconcerns.[92]

In October 2010, CNN published an article titled HappyInformation Overload Day that compiled research aboutemail overload from IT companies and productivity ex-perts. According to Basex, the average knowledge workerreceives 93 messages per day. Subsequent studies havereported higher numbers.[93] Marsha Egan, an email pro-ductivity expert, called email technology both a blessingand a curse in the article. She stated, Everyone justlearns that they have to have it dinging and ashing and

10 9 PROBLEMS

open just in case the boss e-mails, she said. The bestgift any group can give each other is to never use e-mailurgently. If you need it within three hours, pick up thephone.[94]

9.3 Spamming and computer viruses

The usefulness of email is being threatened by four phe-nomena: email bombardment, spamming, phishing, andemail worms.Spamming is unsolicited commercial (or bulk) email. Be-cause of the minuscule cost of sending email, spammerscan send hundreds of millions of email messages eachday over an inexpensive Internet connection. Hundredsof active spammers sending this volume of mail resultsin information overload for many computer users who re-ceive voluminous unsolicited email each day.[95][96]

Email worms use email as a way of replicating themselvesinto vulnerable computers. Although the rst email wormaected UNIX computers, the problem is most commontoday on the Microsoft Windows operating system.The combination of spam and worm programs results inusers receiving a constant drizzle of junk email, whichreduces the usefulness of email as a practical tool.A number of anti-spam techniques mitigate the impactof spam. In the United States, U.S. Congress has alsopassed a law, the Can Spam Act of 2003, attempting toregulate such email. Australia also has very strict spamlaws restricting the sending of spam from an AustralianISP,[97] but its impact has been minimal since most spamcomes from regimes that seem reluctant to regulate thesending of spam.

9.4 Email spoong

Main article: Email spoong

Email spoong occurs when the email message headeris designed to make the message appear to come from aknown or trusted source. Email spam and phishing meth-ods typically use spoong to mislead the recipient aboutthe true message origin.

9.5 Email bombing

Main article: Email bomb

Email bombing is the intentional sending of large volumesof messages to a target address. The overloading of thetarget email address can render it unusable and can evencause the mail server to crash.

9.6 Privacy concernsMain article: Internet privacy

Today it can be important to distinguish between Inter-net and internal email systems. Internet email may traveland be stored on networks and computers without thesenders or the recipients control. During the transit timeit is possible that third parties read or even modify thecontent. Internal mail systems, in which the informationnever leaves the organizational network, may be more se-cure, although information technology personnel and oth-ers whose function may involve monitoring or managingmay be accessing the email of other employees.Email privacy, without some security precautions, can becompromised because:

email messages are generally not encrypted. email messages have to go through intermediatecomputers before reaching their destination, mean-ing it is relatively easy for others to intercept andread messages.

many Internet Service Providers (ISP) store copiesof email messages on their mail servers before theyare delivered. The backups of these can remain forup to several months on their server, despite deletionfrom the mailbox.

the Received:"-elds and other information in theemail can often identify the sender, preventinganonymous communication.

There are cryptography applications that can serve asa remedy to one or more of the above. For example,Virtual Private Networks or the Tor anonymity networkcan be used to encrypt trac from the user machineto a safer network while GPG, PGP, SMEmail,[98] orS/MIME can be used for end-to-end message encryp-tion, and SMTP STARTTLS or SMTP over TransportLayer Security/Secure Sockets Layer can be used to en-crypt communications for a single mail hop between theSMTP client and the SMTP server.Additionally, many mail user agents do not protect loginsand passwords, making them easy to intercept by an at-tacker. Encrypted authentication schemes such as SASLprevent this.Finally, attached les share many of the same hazardsas those found in peer-to-peer lesharing. Attached lesmay contain trojans or viruses.

9.7 Tracking of sent mailThe original SMTP mail service provides limited mech-anisms for tracking a transmitted message, and none forverifying that it has been delivered or read. It requires

11

that each mail server must either deliver it onward or re-turn a failure notice (bounce message), but both softwarebugs and system failures can causemessages to be lost. Toremedy this, the IETF introduced Delivery Status Noti-cations (delivery receipts) and Message Disposition No-tications (return receipts); however, these are not uni-versally deployed in production. (A complete MessageTracking mechanism was also dened, but it never gainedtraction; see RFCs 3885[99] through 3888.[100])Many ISPs now deliberately disable non-delivery reports(NDRs) and delivery receipts due to the activities ofspammers:

Delivery Reports can be used to verify whether anaddress exists and so is available to be spammed

If the spammer uses a forged sender email address(email spoong), then the innocent email addressthat was used can be ooded with NDRs from themany invalid email addresses the spammermay haveattempted to mail. These NDRs then constitutespam from the ISP to the innocent user

In the absence of standard methods, a range of systembased around the use of web bugs have been developed.However, these are often seen as underhand or rais-ing privacy concerns,[101][102][103] and only work with e-mail clients that support rendering of HTML. Many mailclients now default to not showing web content.[104]Webmail providors can also disrupt web bugs by pre-caching images.[105]

10 U.S. governmentThe U.S. state and federal governments have been in-volved in electronic messaging and the development ofemail in several dierent ways.Starting in 1977, the U.S. Postal Service (USPS) recog-nized that electronic messaging and electronic transac-tions posed a signicant threat to First Class mail volumesand revenue. The USPS explored an electronic messag-ing initiative in 1977 and later disbanded it. Twentyyears later, in 1997, when email volume overtook postalmail volume, the USPS was again urged to embraceemail, and the USPS declined to provide email as aservice.[106][107][108] The USPS initiated an experimen-tal email service known as E-COM. E-COM provideda method for the simple exchange of text messages. In2011, shortly after the USPS reported its state of nancialbankruptcy, the USPS Oce of Inspector General (OIG)began exploring the possibilities of generating revenuethrough email servicing.[109][110][111] Electronic messageswere transmitted to a post oce, printed out, and deliv-ered as hard copy. To take advantage of the service, anindividual had to transmit at least 200 messages. The de-livery time of the messages was the same as First Class

mail and cost 26 cents. Both the Postal Regulatory Com-mission and the Federal Communications Commissionopposed E-COM. The FCC concluded that E-COM con-stituted common carriage under its jurisdiction and theUSPS would have to le a tari.[112] Three years afterinitiating the service, USPS canceled E-COM and at-tempted to sell it o.[113][114][115][116][117][118]

The early ARPANET dealt with multiple email clientsthat had various, and at times incompatible, formats. Forexample, in the Multics, the "@" sign meant kill lineand anything before the "@" sign was ignored, so Mul-tics users had to use a command-line option to specifythe destination system.[28] The Department of DefenseDARPA desired to have uniformity and interoperabil-ity for email and therefore funded eorts to drive to-wards unied inter-operable standards. This led to DavidCrocker, John Vittal, Kenneth Pogran, and Austin Hen-derson publishing RFC 733, Standard for the Format ofARPA Network Text Message (November 21, 1977), asubset of which provided a stable base for common use onthe ARPANET, but which was not fully eective, and in1979, a meeting was held at BBN to resolve incompatibil-ity issues. Jon Postel recounted the meeting in RFC 808,Summary of Computer Mail Services Meeting Held atBBN on 10 January 1979 (March 1, 1982), which in-cludes an appendix listing the varying email systems at thetime. This, in turn, lead to the release of David CrockersRFC 822, Standard for the Format of ARPA InternetText Messages (August 13, 1982).[119] RFC 822 is asmall adaptation of RFC 733's details, notably enhancingthe host portion, to use Domain Names, that were beingdeveloped at the same time.The National Science Foundation took over operations ofthe ARPANET and Internet from the Department of De-fense, and initiated NSFNet, a new backbone for the net-work. A part of the NSFNet AUP forbade commercialtrac.[120] In 1988, Vint Cerf arranged for an intercon-nection of MCI Mail with NSFNET on an experimentalbasis. The following year Compuserve email intercon-nected with NSFNET. Within a few years the commer-cial trac restriction was removed from NSFNETs AUP,and NSFNET was privatised.In the late 1990s, the Federal Trade Commission grewconcerned with fraud transpiring in email, and initiated aseries of procedures on spam, fraud, and phishing.[121] In2004, FTC jurisdiction over spamwas codied into law inthe form of the CAN SPAM Act.[122] Several other U.S.federal agencies have also exercised jurisdiction includingthe Department of Justice and the Secret Service.NASA has provided email capabilities to astronautsaboard the Space Shuttle and International Space Stationsince 1991 when a Macintosh Portable was used aboardSpace Shuttle mission STS-43 to send the rst email viaAppleLink.[123][124][125] Today astronauts aboard the In-ternational Space Station have email capabilities via thewireless networking throughout the station and are con-

12 12 REFERENCES

nected to the ground at 10 Mbit/s Earth to station and 3Mbit/s station to Earth, comparable to home DSL con-nection speeds.[126]

11 See also Email encryption HTML email Internet fax Privacy-enhanced Electronic Mail Dark Mail Alliance Push email X-Originating-IP Anti-spam techniques E-card Email art Email storm List of email subject abbreviations Information overload Netiquette Posting style Usenet quoting Bi Email authentication Comparison of email clients Email hosting service Internet mail standards RSS to email Unicode and email Webmail, Comparison of webmail providers Anonymous remailer Disposable email address Email digest Email encryption Email tracking Electronic mailing list Mailer-Daemon

Mailing list archive Telegraphy Lexigram MCI Mail X400

12 References[1] RFC 5321 Simple Mail Transfer Protocol. Network

Working Group. Retrieved 19 January 2015.

[2] Google Ngram Viewer. Books.google.com. Retrieved2013-04-21.

[3] Ron Brown, Fax invades the mail market, New Scientist,Vol. 56, No. 817 (Oct., 26, 1972), pages 218221.

[4] Herbert P. Luckett, Whats News: Electronic-mail deliv-ery gets started, Popular Science, Vol. 202, No. 3 (March1973); page 85

[5] (Partridge 2008)

[6] http://dir.yahoo.com/business_and_economy/business_to_business/communications_and_networking/internet_and_world_wide_web/email_providers/free_email/

[7] ""Email or e-mail"". English Language & Usage StackExchange. August 25, 2010. Retrieved September 26,2010.

[8] RFC Editor Terms List. IETF. This is suggested by theRFC Document Style Guide

[9] Yahoo style guide. Styleguide.yahoo.com. Retrieved2014-01-09.

[10] AP Stylebook editors share big changes from theAmerican Copy Editors Society

[11] Gerri Berendzen; Daniel Hunt. AP changes e-mail toemail. 15th National Conference of the American CopyEditors Society (2011, Phoenix). ACES. Retrieved 23March 2011.

[12] AskOxford Language Query team. What is the correctway to spell 'e' words such as 'email', 'ecommerce', 'egov-ernment'?". FAQ. Oxford University Press. Archivedfrom the original on July 1, 2008. Retrieved 4 Septem-ber 2009. We recommend email, as this is now by far themost common form

[13] Reference.com. Dictionary.reference.com. Retrieved2014-01-09.

[14] Random House Unabridged Dictionary, 2006

[15] The American Heritage Dictionary of the English Lan-guage, Fourth Edition

[16] Princeton University WordNet 3.0

[17] The American Heritage Science Dictionary, 2002

13

[18] Merriam-Webster Dictionary. Merriam-Webster. Re-trieved 9 May 2014.

[19] RFC 821 (rfc821) Simple Mail Transfer Protocol.Faqs.org. 1971-06-11. Retrieved 2014-01-09.

[20] RFC 1939 (rfc1939) Post Oce Protocol Version 3.Faqs.org. Retrieved 2014-01-09.

[21] RFC 3501 (rfc3501) InternetMessage Access Protocol version 4rev1. Faqs.org. Retrieved 2014-01-09.

[22] "''"RFC Style Guide"'', Table of decisions on consistentusage in RFC. Retrieved 2014-01-09.

[23] Excerpt from the FAQ list of the Usenet newsgroupalt.usage.english. Alt-usage-english.org. Retrieved2014-01-09.

[24] USPS Support Panel, Louis T Rader, Chair, ChapterIV: Systems, Electronic Message Systems for the U.S.Postal Service, National Academy of Sciences, Washing-ton, D.C., 1976; pages 2735.

[25] CTSS, Compatible Time-Sharing System (September4, 2006), University of South Alabama, USA-CTSS.

[26] an IBM 7094

[27] Tom Van Vleck, The IBM 7094 and CTSS (Septem-ber 10, 2004), Multicians.org (Multics), web: Multicians-7094.

[28] Tom Van Vleck. The History of Electronic Mail.

[29] IBM, 1440/1460 Administrative Terminal System (1440-CX-07X and 1460-CX-08X) Application Description(PDF), Second Edition, IBM, p. 10, H20-0129-1

[30] IBM, System/36O Administrative Terminal System DOS(ATS/DOS) Program Description Manual, IBM, H20-0508

[31] IBM, System/360 Administrative Terminal System-OS(ATS/OS) Application Description Manual, IBM, H20-0297

[32] Ray Tomlinson. The First Network Email. Open-map.bbn.com. Retrieved 2014-01-09.

[33] Version 3 Unix mail(1) manual page from 10/25/1972.Minnie.tuhs.org. Retrieved 2014-01-09.

[34] Version 6 Unix mail(1) manual page from 2/21/1975.Minnie.tuhs.org. Retrieved 2014-01-09.

[35] APL Quotations and Anecdotes, including Leslie Gold-smith's story of the Mailbox

[36] History of the Internet, including Carter/Mondale use ofemail

[37] David Wooley, PLATO: The Emergence of an OnlineCommunity, 1994.

[38] The Mail Reference Manual, Kurt Shoens, University ofCalifornia, Berkeley, 1979.

[39] An Introduction to the Berkeley Network, Eric Schmidt,University of California, Berkeley, 1979.

[40] Stromberg, Joseph (22 February 2012). A Piece ofEmail History Comes to the American History Museum.Smithsonian Institution. Retrieved 11 June 2012.

[41] Statement from the National Museum of American His-tory: Collection of Materials from V.A. Shiva Ayyadurai(Press release). National Museum of American History.23 February 2012. Retrieved 19 February 2013.

[42] A Mail Handling System, Bruce Borden, The Rand Cor-poration, 1979.

[43] "...PROFS changed the way organizations communicated,collaborated and approached work when it was introducedby IBMs Data Processing Division in 1981... , IBM.com

[44] 1982 The National Security Council (NSC) sta atthe White House acquires a prototype electronic mail sys-tem, from IBM, called the Professional Oce System(PROFs).... , fas.org

[45] Gordon Bells timeline of Digital Equipment Corpora-tion. Research.microsoft.com. 1998-01-30. Retrieved2014-01-09.

[46] with various vendors supplying gateway software to linkthese incompatible systems

[47] Ray Tomlinson. The First Network Email.

[48] Version 7 Unix manual: UUCP Implementation De-scription by D. A. Nowitz, and A Dial-Up Network ofUNIX Systems by D. A. Nowitz and M. E. Lesk. Re-trieved 2014-01-09.

[49] Setting up the Fourth Berkeley Software Tape, WilliamN.Joy, Ozalp Babaoglu, Keith Sklower, University of Cali-fornia, Berkeley, 1980.

[50] Mail(1), UNIX Programmers Manual, 4BSD, Universityof California, Berkeley, 1980.

[51] BITNET History, livinginternet.com

[52] Delivering the Enterprise Message, 19 Sep 1994, DanielBlum, Network World

[53] "...oers improved performance, greater reliability andmuch more exibility in everything from communicationshardware to scheduling... , 03/07/94, Mark Gibbs, Net-work World

[54] MHS: Correct Addressing format to DaVinci Email viaMHS. Microsoft Support Knowledge Base. Retrieved2007-01-15.

[55] Email History. Livinginternet.com. 1996-05-13. Re-trieved 2014-01-09.

[56] The Technical Development of Internet Email CraigPartridge, AprilJune 2008, p.5

[57] Wave New World,Time Magazine, October 19, 2009,p.48

[58] How E-mail Works (internet video). howstuworks.com.2008.

14 12 REFERENCES

[59] Simpson, Ken (October 3, 2008). An update to the emailstandards. MailChannels Blog Entry.

[60] P. Resnick, Ed. (October 2008). RFC 5322, InternetMessage Format. IETF.

[61] Moore, K (November 1996). MIME (Multipurpose In-ternet Mail Extensions) Part Three: Message Header Ex-tensions for Non-ASCII Text. IETF. Retrieved 2012-01-21.

[62] A Yang, Ed. (February 2012). RFC 6532, Internation-alized Email Headers. IETF. ISSN 2070-1721.

[63] J. Yao, Ed., W. Mao, Ed. (February 2012). RFC 6531,SMTP Extension for Internationalized Email Addresses.IETF. ISSN 2070-1721.

[64] RFC 5322, 3.6. Field Denitions. Tools.ietf.org. Oc-tober 2008. Retrieved 2014-01-09.

[65] RFC 5322, 3.6.4. Identication Fields. Tools.ietf.org.October 2008. Retrieved 2014-01-09.

[66] RFC 5064. Tools.ietf.org. December 2007. Retrieved2014-01-09.

[67] Microsoft, Auto Response Suppress, 2010, microsoft ref-erence, 2010 Sep 22

[68] John Klensin (October 2008). Trace Information.Simple Mail Transfer Protocol. IETF. sec. 4.4. RFC5321. https://tools.ietf.org/html/rfc5321#section-4.4.

[69] John Levine (14 January 2012). Trace headers. emailmessage. IETF. Retrieved 16 January 2012. there aremany more trace headers than those two

[70] This extensible eld is dened by RFC 7001, that also de-nes an IANA registry of Email Authentication Parame-ters.

[71] RFC 7208.

[72] Dened in RFC 3834, and updated by RFC 5436.

[73] RFC 5518.

[74] Craig Hunt (2002). TCP/IP Network Administration.O'Reilly Media. p. 70. ISBN 978-0-596-00297-8.

[75] Email policies that prevent viruses.

[76] When posting to a RootsWeb mailing list....Helpdesk.rootsweb.com. Retrieved 2014-01-09.

[77] "...Plain text, 72 characters per line.... Openbsd.org. Re-trieved 2014-01-09.

[78] How to Prevent the Winmail.dat File from Being Sentto Internet Users. Support.microsoft.com. 2010-07-02.Retrieved 2014-01-09.

[79] In practice, some acceptedmessages may nowadays not bedelivered to the recipients InBox, but instead to a Spam orJunk folder which, especially in a corporate environment,may be inaccessible to the recipient

[80] RFC 2368 section 3 : by Paul Homan in 1998 discussesoperation of the mailto URL.

[81] Allen, David (2004). Windows to Linux. Prentice Hall. p.192.

[82] Barrett, Grant (December 23, 2007). All We Are Say-ing.. New York Times. Retrieved 2007-12-24.

[83] Email Right to Privacy Why Small Businesses Care.Anita Campbell. 2007-06-19.

[84] By Om Malik, GigaOm. "Is Email a Curse or a Boon?"September 22, 2010. Retrieved October 11, 2010.

[85] Martin, Brett A. S., Joel Van Durme, Mika Raulas, andMarko Merisavo (2003), E-mail Marketing: ExploratoryInsights from Finland, Journal of Advertising Research,43 (3), 293300.

[86] Matt McGee. March 28, 2013. Email Is Top Ac-tivity On Smartphones, Ahead Of Web Browsing& Facebook [Study]. http://marketingland.com/smartphone-activities-study-email-web-facebook-37954

[87] Jordan van Rijn. April 2014. The ultimate mobileemail statistics overview. http://www.emailmonday.com/mobile-email-usage-statistics

[88] SMEmail A New Protocol for the Secure E-mail inMobile Environments, Proceedings of the AustralianTelecommunications Networks and Applications Confer-ence (ATNAC'08), pp. 3944, Adelaide, Australia, Dec.2008.

[89] Exchange 2007: Attachment Size Increase,.... TechNetMagazine, Microsoft.com US. 2010-03-25.

[90] Lohr, Steve (2007-12-20). Is Information Overload a$650 Billion Drag on the Economy?". New York Times.Retrieved May 1, 2010.

[91] Stross, Randall (2008-04-20). Struggling to Evade theE-Mail Tsunami. New York Times. Retrieved May 1,2010.

[92] Did Darwin Skip Over Email?". Foundry Group. 2008-04-28.

[93] Radicati, Sara. Email Statistics Report, 2010 (PDF).

[94] Gross, Doug (July 26, 2011). Happy Information Over-load Day!". CNN.

[95] Rich Kawanagh. The top ten email spam list of 2005.ITVibe news, 2006, January 02, ITvibe.com

[96] How Microsoft is losing the war on spam Salon.com

[97] Spam Bill 2003 (PDF)

[98] SMEmail A New Protocol for the Secure E-mail inMobile Environments, Proceedings of the AustralianTelecommunications Networks and Applications Confer-ence (ATNAC'08), pp. 3944, Adelaide, Australia, Dec.2008.

[99] RFC 3885, SMTP Service Extension for Message Tracking

[100] RFC 3888, Message Tracking Model and Requirements

15

[101] Amy Harmon (2000-11-22). Software That Tracks E-Mail Is Raising Privacy Concerns. The NewYork Times.Retrieved 2012-01-13.

[102] About.com. Email.about.com. 2013-12-19. Retrieved2014-01-09.

[103] Webdevelopersnotes.com. Webdevelopersnotes.com.Retrieved 2014-01-09.

[104] Outlook: Web Bugs & Blocked HTML Images, slip-stick.com

[105] Gmail blows up e-mail marketing..., Ron Amadeo, Dec13 2013, Ars Technica

[106] http://www.fastcompany.com/1780716/can-technology-save-us-postal-service

[107] http://tech.mit.edu/V131/N60/emaillab.html

[108] http://www.fedtechmagazine.com/article/2013/01/why-united-states-postal-service-taking-cues-silicon-valley

[109] http://cmsw.mit.edu/usps-can-save-itself/

[110] http://bostinno.streetwise.co/2012/01/13/could-email-save-snail-mail-or-is-the-internet-too-reliant-on-the-usps/

[111] http://www.bostonglobe.com/lifestyle/2012/03/02/dear-usps/V4GJ8w9UCcfV4v0WiVjvmK/story.html

[112] In re Request for declaratory ruling and investigation byGraphnet Systems, Inc., concerning the proposed E-COMservice, FCC Docket No. 79-6 (September 4, 1979)

[113] History of the United States Postal Service, USPS, 13November 2014

[114] Hardy, Ian R; The Evolution of ARPANET Email; 1996-05-13; History Thesis Paper; University of California atBerkeley

[115] James Bovard, The LawDinosaur: The US Postal Service,CATO Policy Analysis (February 1985)

[116] Jay Akkad, The History of Email. Cs.ucsb.edu. Re-trieved 2014-01-09.

[117] US Postal Service: Postal Activities and Laws Related toElectronic Commerce, GAO-00-188 (PDF). Retrieved2014-01-09.

[118] Implications of Electronic Mail and Message Systemsfor the U.S. Postal Service , Oce of Technology As-sessment, Congress of the United States, August 1982(PDF). Retrieved 2014-01-09.

[119] Email History, How Email was Invented, Living Inter-net. Livinginternet.com. 1996-05-13. Retrieved 2014-01-09.

[120] Robert Cannon. Internet History. Cybertelecom. Re-trieved 2014-01-09.

[121] Cybertelecom : SPAM Reference

[122] Robert Cannon. Can Spam Act. Cybertelecom. Re-trieved 2014-01-09.

[123] Cowing, Keith (2000-09-18). 2001: A Space Laptop |SpaceRef Your Space Reference. Spaceref.com. Re-trieved 2014-01-09.

[124] The Mac Observer This Week in Apple History Au-gust 2231: Welcome, IBM. Seriously, Too Late to Li-cense. Macobserver.com. 2004-10-31. Retrieved 2014-01-09.

[125] Linzmayer, Owen W. (2004). Apple condential 2.0 :the denitive history of the worlds most colorful company([Rev. 2. ed.]. ed.). San Francisco, Calif.: No StarchPress. ISBN 1-59327-010-0.

[126] Bilton, Nick (January 22, 2010). First Tweet fromSpace. New York Times.

13 Further reading

Cemil Betanov, Introduction to X.400, ArtechHouse, ISBN 0-89006-597-7.

Marsha Egan, "Inbox Detox and The Habit ofEmail Excellence", Acanthus Publishing ISBN 978-0-9815589-8-1

Lawrence Hughes, Internet e-mail Protocols, Stan-dards and Implementation, Artech House Publish-ers, ISBN 0-89006-939-5.

Kevin Johnson, Internet Email Protocols: A Devel-opers Guide, Addison-Wesley Professional, ISBN0-201-43288-9.

Pete Loshin, Essential Email Standards: RFCs andProtocols Made Practical, JohnWiley & Sons, ISBN0-471-34597-0.

Partridge, Craig (AprilJune 2008). The Techni-cal Development of Internet Email (PDF). IEEEAnnals of the History of Computing (Berlin: IEEEComputer Society) 30 (2). ISSN 1934-1547

Sara Radicati, ElectronicMail: An Introduction to theX.400 Message Handling Standards, Mcgraw-Hill,ISBN 0-07-051104-7.

John Rhoton, Programmers Guide to Internet Mail:SMTP, POP, IMAP, and LDAP, Elsevier, ISBN 1-55558-212-5.

John Rhoton, X.400 and SMTP: Battle of the E-mailProtocols, Elsevier, ISBN 1-55558-165-X.

David Wood, Programming Internet Mail, O'Reilly,ISBN 1-56592-479-7.

16 14 EXTERNAL LINKS

14 External links E-mail at DMOZ IANAs list of standard header elds The History of Email is Dave Crockers attempt atcapturing the sequence of 'signicant' occurrencesin the evolution of email; a collaborative eort thatalso cites this page.

The History of Electronic Mail is a personal memoirby the implementer of an early email system

A Look at the Origins of Network Email is a short,yet vivid recap of the key historical facts

17

15 Text and image sources, contributors, and licenses15.1 Text

Email Source: http://en.wikipedia.org/wiki/Email?oldid=664283156 Contributors: Magnus Manske, The Epopt, Derek Ross, LC~enwiki,Lee Daniel Crocker, Zundark, The Anome, Stephen Gilbert, Taw, Chato, Mark, Drj, Ed Poor, NemoThorx, ClaudineChionh, Eclecticology,Gianfranco, PierreAbbat, Fubar Obfusco, Hanoman, Zoe, Daniel C. 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Wozniak, FayssalF, SystemBuilder, Spaceman85, Ysangkok, Who, Nivix, RexNL, Ewlyahoocom, Gurch,RobyWayne, Alexjohnc3, Intgr, TeaDrinker, Butros, Pinotgris, Chobot, DVdm, Digitalme, UkPaolo, Uriah923, YurikBot, Wavelength,RobotE, Hairy Dude, Retodon8, Charles Gaudette, Wolfmankurd, Phantomsteve, RussBot, Me and, Kazikameuk, RadioFan, Stephenb,Tenebrae, Barefootguru, C777, CambridgeBayWeather, Rsrikanth05, Pseudomonas, Wimt, Anomalocaris, Sentausa, NawlinWiki, Drag-onHawk, Hm2k, SEWilcoBot, Wiki alf, Bachrach44, Msikma, Trovatore, Dugosz, Bayle Shanks, Irishguy, Nick, Silvery, Xdenizen, Shep-azu, Bobak, ScottyWZ, Bkil, Nick C, Allynnc, Zwobot, Drumsac, BOT-Superzerocool, DRosenbach, Xpclient, Wknight94, Novasource,NormDor, Sandstein, Phgao, Zzuuzz, Closedmouth, 6a4fe8aa039615ebd9ddb83d6acf9a1dc1b684f7, Ka-Ping Yee, Reyk, Ray Chason,JuJube, SCGC, Lordmac, Nelson50, JLaTondre, Spooksh, Ilmari Karonen, Eaefremov, Aliza250, Mdwyer, NeilN, GrinBot~enwiki, As-terion, SkerHawx, DVD R W, Veinor, SmackBot, Unschool, Classiclms, Faisal.akeel, Jlandis~enwiki, KnowledgeOfSelf, Bigbluesh,Gribeco, Pgk, Randallrobinstine, Blue520, Bomac, KocjoBot~enwiki, Thunderboltz, Anastrophe, Hew~enwiki, Eskimbot, Hardyplants,MindlessXD, CapitalSasha, Canthusus, Lomonline, MelancholieBot, Yamaguchi, Unforgettableid, Ignacioerrico, Gilliam, Ohnoits-jamie, NickGarvey, Anwar saadat, Kaliumfredrik, TimBentley, Parmesan, Jprg1966, Fatbroker, Thumperward, Snori, EncMstr, Chiso-phugis, Nbarth, Omniplex, KC., Darth Panda, A. 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Ric, Harryzilber,Pipedreamergrey, Adamcox82, MER-C, Skomorokh, Minitrue, Lathama, John a s, Hello32020, Sroeben, Martinkunev, 100110100, Sirp-ing, PhilKnight, Comodo, Bearly541, Yahel Guhan, Wasell, SteveSims, Z22, Magioladitis, Bongwarrior, VoABot II, AtticusX, Trnj2000,JamesBWatson, CattleGirl, Tedickey, CTF83!, Nxu009, Twsx, Cglenn3932, Avicennasis, DXRAW, Bubba hotep, Rohasnagpal, Mwal-imu59, Peschomd, 28421u2232nfenfcenc, Styrofoam1994, Mike Payne, Cpl Syx, Dr Pukhtunyar Afghan, Smpwiki, Chris G, Zivha,DerHexer, Not telling, Jodi.a.schneider, Rbpickup, Prozac1980, Makro, MartinBot, Vigyani, Blitzinteractive, Zip123, Philhower, RedSunset, Naohiro19, Ibizr, Krushdiva, Rettetast, Anaxial, Zouavman Le Zouave, Mschel, AlexiusHoratius, Lucasik~enwiki, Patar knight,Lilac Soul, Emailexperiencecouncil, Pomte, Garkbit, Emily GABLE, Doc marseille, Manticore, J.delanoy, Pharaoh of the Wizards, Trusil-ver, EscapingLife, Numbo3, Safedoctor~enwiki, Tikiwont, Darkride, Jesant13, Sidhekin, Extransit, Neon white, Gzkn, Andareed, Kata-laveno, Thomas Larsen, Grosscha, Silas S. 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18 15 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

Your Car, Mrlee321, Vituzzu, C'est moi, Anchor Link Bot, Dhoom4, Maralia, Yuva raju raj, Denisarona, Joel Rennie, Heinzi.at, Hoplon,WikipedianMarlith, Twinsday, ClueBot, Agent2693, WilliamRoper, Mhackmer, PipepBot, MWelchUK, The Thing That Should Not Be,Unbuttered Parsnip, Joeldbenson, Arakunem, Startvtk, Meekywiki, VQuakr, Mild Bill Hiccup, TheOldJacobite, Lisabelleg, Niceguyedc, , Nebula17, Pat80, HMBot~enwiki, Melizg, DragonBot, Gnome de plume, Jusdafax, Sean 1996, Smtc123, Leonard^Bloom,Dr.s.t.ruggling, Muhandes, KnowledgeBased, Lartoven, Sun Creator, Crackerwashere, Thuja, Asdasd12324, Jotterbot, Cmartell, El pobrePedro, Razorame, Durcar86, Galaxy250, Inspector 34, Bald Zebra, Armando49, Thingg, Callmejosh, Aitias, 7, Sd324, Eliezer Aharon,Crazyperson324, PCHS-NJROTC, Canihaveacookie, Johnuniq, SoxBot III, Goodvac, Pivotrock, DumZiBoT, Lunboks, RaphelM.Markez,XLinkBot, Prof Wrong, Will-B, Emmy.rose, Pichpich, Pgallert, Avoided, Sogle, Skarebo, WikHead, SilvonenBot, Mifter, Frood, Alex-ius08, Mm40, Mozillar, Param0r33, HexaChord, Merry Devil, Mogglewump, Prowikipedians, Addbot, Xp54321, Grayfell, Willking1979,Some jerk on the Internet, Jafeluv, Mabdul, Aspandphp, EjsBot, Iceblock, PatrickFlaherty, Boomur, CellMan0677, Fieldday-sunday, Kar-camp, Bnorrie, Ilya-108, Fluernutter, Nickhonner, Skyezx, Foodlol123, Protonk, Ccacsmss, Jomunro, Arjuno3, Cutechar, Jasper Deng,Lineface, Mystical504, Davecrocker, Tide rolls, Pernoctus, MelcomRSA, Lightbot, OlEnglish, Jan eissfeldt, Ghemachandar, SasiSasi,Thebigmc2, Taargus taargus 1, Frehley, Dreammixtr, Legobot, Luckas-bot, Smokyjohnpipe, Yobot, 2D, Dhaun, Dede2008, Fraggle81,TaBOT-zerem, Gollobt, Legobot II, Newportm, Cyanoa Crylate, Jjl33, ArchonMagnus, THEN WHO WAS PHONE?, Fisc, Timir Saxa,Evaders99, , Eric-Wester, AnomieBOT, Dangerousdanman, Suri252001, AMore Perfect Onion, Hairhorn, Roland45~enwiki,Stolen Account 1, IRP, Galoubet, Piano non troppo, Sorsoup, 90, AdjustShift, Skpatel20, Kingpin13, Materialscientist, , A123a,Maxis ftw, Woods229, Neurolysis, Chivasboi345, ArthurBot, LilHelpa, Obersachsebot, Nehtefa, Xqbot, TheAMmollusc, Agather, Sionus,Mr. Prez, Melmann, Capricorn42, Drilnoth, Johnny Bin, Hobomason, Alanpratt05, Shaior, MccowattMAS229, Tad Lincoln, Grim23, Pro-gramarium, Jmundo, Slowbuteective, Cboy676, AbigailAbernathy, Jaizanuar, Comm 212 8, C+C, GrouchoBot, Ute in DC, Wizardist,Shirik, Mark Schierbecker, RibotBOT, SassoBot, Cresix, Wikieditor1988, Amaury, Ivan Shmakov, Hymek, Kikodawgzzz, Stratocracy,Doulos Christos, Shadowjams, Chatul, Gnuish, Douglas W. Jones, Jinxynix, PM800, Boyhampus, RetiredWikipedian789, GliderMaven,George2001hi, FrescoBot, Bigderom, Nageh, Merciadriluca, Atas76, Cameforu, Farawayfrom, Skylerfatfacewrwe, Sexdemon89, Pork-chop28, Youarefunny, Citation bot 1, EagleEye96, Buckinghampalace101, Redrose64, Pinethicket, I dream of horses, HRoestBot, 10me-treh, Jonesey95, Tinton5, Cafeduke, RedBot, Olivier Bommel, Davidx2, Beao, Xwildre316x, Merlion444, December21st2012Freak,----, Classfun, Martaw22, TobeBot, Trappist the monk, FFM784, Dragory, Lotje, Vrenator, Antoine854, Clarkcj12,Henry hedden, Sarasvathi, Joshhirstwood, Notsocoolkid, Weedwhacker128, Tbhotch, Minimac, Sideways713, Mean as custard, Rjwilmsi-Bot, Liamzebedee, Alph Bot, Liamob1993, Bobzayton489, Regancy42, Vaikulepak, Camarac, EmausBot, John of Reading, Orphan Wiki,Racerx11, Mbekula, Freeaqingme, RA0808, WJake2009, RenamedUser01302013, Tommy2010, Lonestarcowboy, Wikipelli, Benq2010,Iainh, Checkingfax, Ida Shaw, Illegitimate Barrister, Ramrod 63, , Ionidasz, Battoe19, EJavanainen, Jallar, Chithrapriya, Encyed-itor, Wayne Slam, Tailchopper99, Erianna, Chadude, Mursyids, Demiurge1000, W163, Augurar, Brandmeister, L Kensington, Schnoat-brax, Donner60, Agheefner, SPAMSLAVE, Moshi Monster Fan303, David Rolek, Noggo, Shaxelen, Bomazi, ChuispastonBot, Rock-Magnetist, Bad edits r dumb, Teapeat, DASHBotAV, Wikiwiki3010, 28bot, Sfung256, Rdowne52, Petrb, LM2000, Comm151student,ClueBot NG, Gabeharvell123, Smtchahal, Better email better life, Erik Lnnrot, Gareth Grith-Jones, Joemcboi, MelbourneStar, Thislousy T-shirt, Bulldog73, Mykebrett, Chester Markel, Another n00b, Snotbot, Ronstauerjr, Frietjes, Cntras, Vlhsrp, Jem2011, Widr,Bshurtz, Michiyoo, Wikiwhalley, Rom1sub, LBM2388, Helpful Pixie Bot, Hovn~enwiki, HMSSolent, Ukrstar, Calabe1992, Wbm1058,Spurple, BG19bot, Xsava, Talha hasan1992, Mmwaseermohamed, Northamerica1000, Wzrd1, Doctorrace, Tomattheworthington, Ed-wardZhao, Hallows AG, Aktrelly, Aztrelly, Shady529, Wiki13, Chafe66, Derekmciver, Who R you?, Mark Arsten, Emailxpert, Altar,Vashiva, Crazyparty16, Test1324, DGRichard, YoterMimeni, Earendil56, Matbury, Achowat, Rhaegor, Proxyma, Ahmahran, Arcandam,Khazar2, Umpienl, MadGuy7023, Vince001001, Andrew Eugene, Openhost101, Akell567, AlexBuzaev, Mogism, 247email, Derekvi-cente, Dlong48, A53collins, Lugia2453, Frosty, Granichk, Davidvail, Zziccardi, Snehakmurthy,WiHkibew, Corn cheese, Scuzzawuzza123,Raj Singh, Reatlas, BurritoBazooka, BeachComber1972, Ekips39, Kswcarey, Faizan, Kerala01, Comm212gr5, Alitlebitsexy, I am Oneof Many, Mattsabe, Rockonomics, Petemclaren, Eyesnore, Jodosma, Ryanluck3, Fernwood1990, CSN13, Syamsunders, Pizzasaver,Reedjc, MaxBowsher, Boconn45, Shahnamk, Citrusbowler, Ginsuloft, Jmjmjmie, Bodekaer, Larrysextape, Abhijith anil, Lagoset, St170e,Gmoye101, Monkbot, AlexBuzaev82, Josie1982thebb, Jarbygardeenyia, Leegrc, Jwhite1336, Grovind2000, Hlevy2, Ksurquhart, Mad-man123467, User26954344524345, Allgrace20, Deonikar, CamelCase, TechJimmyMack, Jinx65555, TVleck1971, Titch-hamilton99 x,TranquilHope, KH-1, Mario Casteln Castro, Hollyrood, Rileyandangandelle, Jawad Ashraf Warraich, IRW0, Nathangilreath11, IPUp-cia, Edawmail, Iwilsonp, TeaLover1996, Tuihjbnb, Rin borum, Reaganomics88, Jhennessy91, Rtc321, TrippieHippie, Baya younes, Getat-ech and Anonymous: 1409

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