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電子 メ ー ル
Through part of the internetRouting pathVisualization of
電子 メ ー ル(Denshi Mail, English: Electronic mail, E-mail,Email) IsComputer networkIs a means of exchanging information, etc., using a mail.Electronic mailAlso called (Denshi Yubin).
On the other hand, before the spread of the Internet, so-calledPC communicationHowever, a system for exchanging documents between subscribers was provided as "e-mail". However, in personal computer communication, since communication was generally limited to one personal computer communication system, there was almost no mutual communication function such as an e-mail exchange function with another system. Also, since there were many cases where each PC communication system had its own system,User interfaceAnd so onCompatibleThere was no However, since then, with the spread of the Internet, it has become possible to communicate between major personal computer communication systems and the Internet. Email friend (Mel friend), there were times when it became fashionable.
In the following, items that are not described as "broadly defined mail" areRFCDescribes only e-mails that use the UUCP and SMTP protocols, which comply with. For other emails, see the related items above.
Email in a narrow sense
- RFCE-mail that conforms to the UUCP and SMTP protocols.
- Email viewed by logging in to another computer (server, host)- clientTerminal software (Web browser,telnetE-mail that does not require software other than devices (such as terminals). It is transmitted to the server in a method that complies with RFC.WebmailIs an e-mail in a broad sense and was usedFree mail serviceIs also popular.
- Electronic bulletin board (BBS),BlogComments-There were novices who called them "mail" when (or even today) the Internet was popular.
- Short message service(SMS) - Mobile phoneVery short between etc.articleSend and receive,i-modeIt has been done before the start of services such as.
- Internet election campaignEmail at- Ministry of Internal Affairs and CommunicationsBy definition, RFC-compliant mail and short message service are defined as mail.
Technologies that support e-mail
For individual emailsア ド レ スIs "
Yamada.Tarou@example.wikipedia.orgIt is expressed in a form such as ". Unique to actually use emailDomain name(In this example,
example.wikipedia.org)) get and manage the domain nameDNS server,Mail serverMost of the time you need to register with.
Although there is no theoretical limit to the capacity, the maximum capacity that can be transmitted and received is limited by the capacity provided by the provider. In general,Dial-up connectionNumber of remnants of the timesMegabyte(MB)BroadbandIn correspondence with the large capacity, 100MB to several GB(Giga(Byte) is often set[Source required].. As an example of major providersOCNUp to 10MB,So-netUp to 20MB,BiglobeIs up to 100MB.. For exchanging large amounts of dataFTP,P2P,HTTPBy etc.online storage,File transfer service,UploaderAnd so on.
Currently on the Internet,Mail serverCommunication betweenclientIs generally sent fromSMTPIs used. In the old days and even now, rarelyUUCPIs used. EmailsserverTherelayIs sent to the target mail server via. In addition, the e-mail includes the e-mail software used by the sender and the transit server.HeaderInformation is attached.
When reading mail from the mail server,POP,IMAPAnd other protocols are used. The format of mail is specified in RFC 5322. Also, non-English characters言语,textFor sending information other than by email, etc.MIMEIs stipulated.
Former JapanJUNETThen.JIS standardSet rules based onJapaneseI was able to handle.. This ruleMIMERedefined in the framework ofISO-2022-JPIs. This ISO-2022-JP is widely used in current Japanese mail.
RFC 2277So I urge you to choose a widely known character code as much as possible. this isUTF-8Is provisional until it becomes widespread, but since it may be 50 years, it is also said that it may be considered as eternal in nature..
Originally, the email wasarticleDegree ofPlain text形式It was only the thing of the above, but aboveMIMEWith the provision and popularization ofHTMLDescribed byHTML mailAlso,RFCIt has been specified by the and has been used by the general public.
HTML emails can be written in HTML because the email text can be written in HTML.Web pageThere is an advantage that it has the same expressive power as.Mobile phone-PHSBut,cHTMLSome form of e-mail is provided as a general-purpose service.
On the other hand, in particular,Microsoft Windows And its standard email client Outlook ExpressWith the spread of (HTML format is selected by default when composing emails), HTML format emails are often sent and received. However, in the mail client, it is necessary to expand and display the HTML information in the mail.Rendering engine(Internet ExplorerWeb browsers such asSecurity holeHas been discovered, just look at (preview) the email,Computer virusIs damaged,spam-Fictitious billingImage by email etc.TagSend and display the email with the embedded, and collect the information that displayed the email (Web beaconSay) and abuseSecurityThere is a problem above (however, "displaying HTML mail" is not technically fundamentally different from "displaying a web page in a browser"). As a measure,Antivirus-Spam measures OfsoftIntroduce or refuse to receive HTML mail with the filtering function / TrashfolderThere are things like sorting to. In addition, some mail clients do not support HTML mail display, so even if you send HTML mail without notice, it may not be received correctly.
In addition, when sending a certain file data as an attachment to an email, it is converted into a text by MIME etc. as an attachment file (Encoding), embed it in the email body, send it, and restore it to the original data file on the receiving side (Decode) Method is taken. Since a computer virus can be loaded in the attached file, if the setting is such that the attached file is automatically opened when received, there is also a risk that the computer virus may be damaged.
Each email is separate from the body of the email.HeaderfieldIt has an area where various special information called is written. Most mail clients can refer to the information in this header field in some way (different for each mail client). This information isIntimidationEmail orス パ ムThis is useful for identifying the sender when you receive an email such as. However,CamouflageHowever, it is not possible to completely judge it because it is not necessary to add all the header fields.
Typical header field
Header fields Field name
:Field value It is described in the form.
- Cc is a copy recipient(32.08.04), Bcc is a secret recipient(32.08.05)Recipient's email address. It can include single or multiple names and addresses.#Cc and BccSee.
- Date and time the sender sent
- Author's email address.. It can include one or more names or addresses.
- The description of this header can be freely changed by the sender by setting the mail client. Due to such email specifications, it is difficult to completely prevent misuse such as so-called "spoofing".
- List of Message-ID values such as reply source mail
- Unique number attached to each email
- MIME version
- By the time this email arrivedMail transfer agent(IP address) And date and time passed
- E-mail address that sender wants to reply to
- E-mail address transmitted as the sender in SMTP communication
- Sender's email address.. The name can be included. It should not be used when the author and sender are the same, that is, From is a single address and is the same as Sender. On the contrary, if different, it is essential.
- A short sentence that describes the topic. In case of replyRe:, In case of transferFw:Is often added to the beginning automatically (#Re and FwSee).
- Recipient's email address. It can include one or more names or addresses.
- Sender's domain
- Global IP address of sender
- Type of mail client
- Severity specified by sender
- eml format: 1 email 1File
- mbox: Combining multiple emails into one file (1 folder and 1 email for each user)
- maildir: 1 mail 1 file
- MH:: 1 mail 1 file is similar, but directory specifications are different
Cc and Bcc
As a function when sending mail,
Bcc(Secret recipient(32.08.05)) There are two types. The original destination of the email is generally specified as To: and sent, but this function is used when there is a person other than the original destination who wants to send a copy.
Of course, people who are new to e-mail as well as people who are already used to it often do not understand the original usage of this function.[Original research?].. It is very convenient to use this function if you understand and use it well, but it is not limited to private and public use, the difference between Cc function and Bcc function If you do not understand and use the destination well,personal informationIt causes problems in various ways such as leakage.
BccSince there are mail software with defects such as showing the mail address specified as to other recipients and writing it in another area in the header,
BccSome users understand the function but do not use it[Source required].
ToThis function is used when there are other parties who want to send a copy in addition to the original destination specified in.
ToIn the same way as specifying the destination with,
CcSpecify the person you want to send a copy to and use it.
ToTo the original opponent specified in
CcYou can see all the destinations specified in. Also,
CcTo the person specified in
CcYou can see all the destinations specified in.
- In short, the sender (
CcThe address will be known to all three people.
ToThere are other people who want to send a copy in addition to the original destination specified in.
CcThis function is used when you do not want to know the email address of the person who sent the copy and the fact that the copy was sent to the person specified in.
ToIn the same way as specifying the destination with,
BccSpecify the person you want to send a copy to and use it. When forwarding mail
BccSince the header is deleted from the email text (SMTP DATA),
CcTo the person specified in
BccThe destination specified for is invisible at all. But,
BccTo the person specified in
CcYou can see all the destinations specified in.What this means is
BccIf the person who received it inadvertently replies with Reply-all,
BccWhat I was doing
CcIt means that it will be known to the recipients of.
BccDepending on the implementation of
CcBy using the format to forward the email sent in, even if you inadvertently do this,
FromIn some cases, emails can only be sent to the person in question.What side effects do you have
BccCareful attention should be paid when using.Also,
BccIf there are multiple destination addresses for
BccAmong the specified destinations, other destinations other than oneself cannot be known.
- When connecting to a single mail account server from multiple mail clients, there is a technique that utilizes Bcc.
FromBy specifying the same address as (yourself) (always setting by mail client (MUA) is also possible), the mail you sent will be delivered to the inbox of your mail client as it is. By setting the mail server to not remove the mail received by the server or mail client on the mail server such as POP3 (delete it after several days), the mail sent from one mail client will be sent to all other mail clients. Delivered as a copy. This allows you to check sent mails with multiple mail clients, where you normally can't know unless you see the sent box of the sent mail client.
- NetiquetteAlthough it is the recommended method of sending emails as one of the above, it is not so true when mass email should use Bcc in any case. For example, for a particular broadcast email, there is no need to use Bcc if all the recipients exchange email addresses, rather To and the destination and purpose are clearly stated. It is normal to use Cc properly. Advanced netiquette knowledge is required to properly use To, Cc, and Bcc depending on the time and case.
- Sometimes, "Black carbon copyIs sometimes said, but it is a mistake, and "blind carbon copy" is correct.
Re and Fw
- Re (Reply)
- manyEmail clientThen, the symbol of Re: or RE: is automatically added to the beginning of the subject of the returned email. This abbreviation is for convenience of automatically adding the reply title "About XX" (Regarding ~) to the title "XX" of the received mail, and is not a mark indicating that it is a reply. The person may intentionally delete it. The conventions used in commercial texts for a long time were adopted for the email commands in the beginning of email, andRFCIt was established by being described in, but there are other theories.
- Fw, Fwd(transfer)
- Part ofEmail clientThen, when forwarding an email, a subject such as Fw: may be automatically added to the beginning of the subject. This abbreviation is not only a matter of convenience like Re, but also a proprietary specification that is not described even in RFC. For example, if Fw: is consecutive, you can think of it as an email that was forwarded many times.Email clientIt's just a specification, not a general understanding. The sequence of Fw:Chain mailSince it is very common, it can also be used as a standard for chain mail. For this reason, some chain mails include instructions to delete Fw: when transferring.
The way to electrically convey text messages was in the mid 1800sMorse codeCan be traced back to the telegram.1939 New York World's FairThen,IBMSent a blessing document from San Francisco to New York by communication using high-speed in-house radio waves that will replace postal mail in the future.Second World WarUsed by GermanyTeletype terminal The,afterwardstelexWas used until the end of the 1960s, when it became popular worldwide. There was a similar TWX in the United States, which occupied the position of an important communication method until the end of the 1980s..
Origin of email
Email was developed before the Internet. The existing e-mail system has become an important tool in making the Internet.
The first email is1965,main frameupperTime sharing systemHas started to be used as a way for multiple users to communicate with each other. By the early 1970s,US Department of Defense Of (AUTODIN) connects 1350 terminals and can handle an average of 1 million messages per month for 3000 million messages per month. The AUTODIN is supported by 3000 computerized large switching devices, and connects about 18 terminals.Also connected to the Advanced Record System.. Although the exact point is unknown, SDC (Land InstituteFrom a spin-off fromSAGEThere is a Q32 system from the company that developed the software.Massachusetts Institute of TechnologyWas in 1961CTSSIntroducedEstablished a system in which multiple users can log in to the central system from a remote terminal using a telephone line, and save and share files on a disk.. E-mail was soon extended to "network e-mail" for users to exchange information between different computers.1966Was forwarding emails between different computers (the details of SAGE are not clear, but it may have happened earlier).
- 1968: Terminal system for office management (IBM) ATS/360
- 1974:PLATO IV Notes-OnlineInternet communityEmail was widely used in the system to notify "personal attention".
- 1981:IBM OfficeVisionPROFS
- 1982:Digital Equipment Corporation OfALL-IN-1
ARPANETHas had a great impact on the evolution of email. Right after its birth1969Has reported that an experiment of inter-system e-mail transfer was conducted..BBN OfRay Tomlinson The1971For the first time to develop an e-mail system on ARPANET@Enabled to specify user name and device using.. The number of e-mail users has increased rapidly on ARPANET,1975Had been used by over 1000 people.
Penetration of the general public
As the convenience and benefits of e-mail on ARPANET became generally known, e-mail became popular and people who could not connect to ARPANET demanded it. Several e-mail systems have been developed that connect time-sharing systems with alternative networks. For exampleUUCP,IBMVNET etc.
All ofComputer,Computer networkSince they are not directly connected to each other, the e-mail address needed to indicate the "route" of information transmission, that is, the path from the sending computer to the receiving computer. Emails can be routed between several networks (ARPANET,Bitnet,NSFNET). It was possible to exchange e-mail with the host connected by UUCP.
The route was specified by a method called "bang path". Write the address of the host that is directly reachable from one host, then bang the address of the next reachable host from it (Exclamation point=!It is an address specification method that connects with) and writes..
CCITTIn the 1980s to enable interoperability of various email systems.X.400Developed a standard. At the same time,IETFIs a simpler protocolSimple Mail Transfer Protocol Developed (SMTP), which is for email transfer on the Internet.De facto standardBecame. In the modern age of connecting to the Internet from homes, the interoperability of e-mail systems based on SMTP is, on the contrary, a security problem.
1982,White House TheAmerican National Security Council (NSC) Adopted IBM's e-mail system Professional Office System (PROF system) for workers.1985In April, the system became fully operational for NSC workers.1986In November, the rest of the White House went online. Until the end of the 11s there was only a PROF system, but after that various systems have been introduced (VAX A-1 (all-in-one), cc:Mail, etc.)
Since 1984 in JapanJUNETHas begun to connect between universities, and has since expanded to include corporate research institutes.Initially, only ASCII characters were assumed, but later in JUNET, a character encoding method that enables the use of Japanese (Kanji) in e-mail, etc.ISO-2022-JPIs being developed(Email # character code).
When composing mail on UNIX as of the late 1980sJapanese input system(FEPAlso called) in a UNIX environmentWnnThere was a way to use (as a Japanese input system, laterCaneWas also developed).Apart from that, on MS-DOSSerial portFor the purpose of communication viaKEK-KermitEtc. and set the personal computer as a UNIX terminal, As a Japanese input systemATOKOrMatsutakeIs used to generate the kanji code on the personal computer side, and KEK-Kermit etc. is used to generate the kanji code on the local side of the personal computer. Shift JIS Is the kanji code specified on the UNIX side.EUCOrJISThere was also a method of inputting kanji when composing an email on UNIX by sending it to the UNIX side while converting it to.Conversely, when displaying an e-mail containing kanji received on the UNIX side on the personal computer side that is the UNIX terminal, the kanji code received on the personal computer side is displayed again by KEK-Kermit etc.Shift JISIt was displayed after being converted to.
In the era that followed, personal computers were directly connected to Ethernet at universities and companies, and dial-up connections were expanding to ordinary households.Email clientAppears.
Increased traffic and delivery delay
Much of the email traffic is actuallySpam mail.Barracuda NetworksReport ofaccording to,200790% to 95% of the emails sent were spam emails. These spam emails, which are sent in large quantities, place an excessive load on the mail server and may cause delays in mail delivery. For example2004From late July to early August, major internet providers@niftyIn spite of this, spam mail sent in large quantities from overseas placed an intermittent burden on the mail server, and continued to hinder the reception of mail... (October 2010ロシアThe spam mailers caught in the U.S. sent 1 billion emails a day. )
In recent years,Trojan horseSuch asMalwareThe ratio of DDoS type spam transmissions caused by computer infected with virus is increasing rapidly, and it is said that the load on mail server will be further increased (→BotnetSee).
Other than spam, there are also so-called "New Year's mails" (a large amount of greeting mails that occur around New Year's day) as a cause of increasing traffic. In particular, e-mail functions such as mobile phones may be used as a chat as a “means for immediate communication”, so they are more likely to be sent in large amounts and more intensively than general e-mail, and delivery due to this Delay orconvergenceMay be a problem. As a countermeasure against this, each telecommunications carrier may call for refraining from use during the year-end hours or restrict calling. In the days when personal computer communication was at its peak, there was also a service to prevent the concentration of processing by sending a New Year's mail reservation to a server in advance and delivering it to New Year's Day.
Note that many e-mail delivery systems have a mechanism in which when the mail server is overloaded with a certain amount of load, the sending is suspended, the data is temporarily stored in the spool, and then resent (for example, several hours later), so that the traffic is Exceeding a certain amount causes extreme delay in delivery. This delay occurs for each email, so even if the emails are sent at the same time, some will arrive in a few seconds, and some will arrive in a few hours. Then, there is a risk of rubbing the email "sent" or "not sent".
一時 的 なtrafficWith the increase ofspoolIn many cases, the pending mail stored in is processed and returns to normal, but if the capacity of the mail server is not sufficient, the resending process itself may not be in time and the failure notification may be returned to the sender.In principle, even a failure notification cannot be returned and "disappeared". If the mail server cannot catch up with the ability to receive mail (SMTPThis is because the connection) itself is rejected. I often see in New Year's mail, etc. that the provider's mail was lost due to increased traffic, as if it were force majeure, but to be exact, the provider's mail server was not properly managed. , The process at the time of congestion is not working properly. The system is defective.[Source required]
Terrorist attacksAt times, there was a one-day delay in mail between New York, and in 1South AfricaでCape TownとJohannesburgExperiments were carried out over 700 km, and the carrier pigeon was able to transmit information earlier than e-mail.
Problems with anti-spam mail
dialectEven people who cannot communicate verbally due to such reasons can communicate with each other by letters, so it is useful to communicate by e-mail in the present age when people's exchanges are widespread (Japan, Japan,Chugoku,The United KingdomEspecially in countries with various dialects). on the other hand,PC communication,インターネットProblems seen in exchanging only characters in etc. (Burning,Flaming) Can also be found in email. There are cases in which the true intentions and emotions of emails do not get transmitted to the other party and often develop into rubbing. In the English-speaking world, the name of an email sent by mistakenly reading the true meaning of the email and leaving it to the emotion (Slang) Has Flame Mail.
Text-based plaintext in email isserver,networkHighly likely to be sniffed abovesecurityIt cannot be said that it is preferable from the viewpoint of.Philip ZimmermannDeveloped and published byCiphersoftware(Pretty Good Privacy: PGP) plug-in etc. can be installed to improve safety.
- ^ "RFC 5321 --Simple Mail Transfer Protocol". Network Working Group (June 2008). Year ending March 2010Browse.
- ^ OCN setting support... OCN email transmission capacity is usually up to 10MB
- ^ So-net member support... Basic mailbox capacity and storage period
- ^ BIGLOBE mail specifications
- ^ a b JUNETUser's Guide (First Edition)
- ^ Using International Characters in Internet Mail[Broken link]
- ^ a b c d e JISX0032 1999.
- ^ "Email address" here is technically called a mailbox-list. The same applies to BCC, CC, Reply-To, To.
- ^ The "email address" here is technically called a mailbox.
- ^ British: carbon copy
- ^ British: blind carbon copy
- ^ British: black carbon copy
- ^ British: forward
- ^ The Watsons: IBM's Troubled Legacy
- ^ See File: Gestapo anti-gay telex.jpg
- ^ Telex and TWX HistoryDonald E. Kimberlin, 1986
- ^ Ron Brown, Fax invades the mail market, New Scientist, Vol. 56, No. 817 (Oct., 26, 1972), pages 218-221.
- ^ Herbert P. Luckett, What's News: Electronic-mail delivery gets started, Popular Science, Vol. 202, No. 3 (March 1973); page 85
- ^ a b USPS Support Panel, Louis T Rader, Chair, Chapter IV: Systems, Electronic Message Systems for the US Postal Service, National Academy of Sciences, Washington, DC, 1976; pages 27-35.
- ^ "CTSS, Compatible Time-Sharing System" (September 4, 2006), , USA-CTSS.
- ^ Tom Van Vleck, "The IBM 7094 and CTSS" (September 10, 2004), Multicians.org (Multics), web: Multicians-7094.
- ^ IBM (pdf). 1440/1460 Administrative Terminal System (1440-CX-07X and 1460-CX-08X) Application Description (Second Edition ed.). IBM. H20-0129-1 2013th of February 2Browse.
- ^ IBM System / 36O Administrative Terminal System DOS (ATS / DOS) Program Description ManualIBM. H20-0508
- ^ IBM System / 360 Administrative Terminal System-OS (ATS / OS) Application Description ManualIBM. H20-0297
- ^ Version 3 Unix mail (1) manual page from 10/25/1972
- ^ Version 6 Unix mail (1) manual page from 2/21/1975
- ^ APL Quotations and Anecdotes, including's story of the Mailbox
- ^ History of the Internet, including Carter / Mondale use of email
- ^ David Wooley, PLATO: The Emergence of an Online Community, 1994.
- ^ Stromberg, Joseph (February 2012, 2). “A Piece of Email History Comes to the American History Museum". Smithsonian Museum. 2012th of February 6Browse.
- ^ "...PROFS changed the way organizations communicated, collaborated and approached work when it was introduced by IBM's Data Processing Division in 1981...", IBM.com
- ^ "1982 --The National Security Council (NSC) staff at the White House acquires a prototype electronic mail system, from IBM, called the Professional Office System (PROFs) ....", fas.org
- ^ Gordon Bell's timeline of Digital Equipment Corporation
- ^ Tom Van Vleck (February 2001, 2). “The History of Electronic Mail". 2008th of February 2Browse.
- ^ Ray Tomlinson. "The First Network Email". 2008th of February 2Browse.
- ^ Version 7 Unix manual: "UUCP Implementation Description" by DA Nowitz, and "A Dial-Up Network of UNIX Systems" by DA Nowitz and ME Lesk
- ^ "BITNET History", livinginternet.com
- ^ rfc976 https://tools.ietf.org/html/rfc976 UUCP Mail Interchange Format Standard Section 5 “Summary” describes the bang path (representing the email address by connecting the host name with!). An example of a bang path is hosta! Hostb! User.
- ^ Hiroshi Kimura, Akihiro Taimura "How to use e-mail and electronic news"Bulletin of the Faculty of Liberal Arts, Nagasaki University, Natural Sciences," Vol. 33, No. 1, Nagasaki University, Faculty of Liberal Arts, July 1992, pp. 7-65, ISSN 02871319, NOT 120000916619., "5.1 Setup between modem (digital phone) and computer"]
- ^ Yukihiro Katsumura (December 2007, 12). “"95% of emails were'junk emails'", 2007 spam trends". ITpro. Nikkei BP. 2008th of February 2Browse.
- ^ "Member support> About mail delay due to mass spam mail and countermeasures". @nifty. Nifty (September 2004, 8). 2008th of February 2Browse.[Broken link]
- JIS X 0032: 1999 "Information Processing Term-Email"(Japanese Industrial Standards Committee,Ministry of Economy, Trade and Industry）
- Email Address
- e-mail magazine
- Free mail service
- Push email
- Web mail
- Career mail
- Mailing list
- Mail server - Domain Name System(DNS)
- Email client(E-mail software, mail client, MUA)
- Spam (email)(spam)
- Chain mail
- Store and forward
- mailto:(TO) (scheme）
- CC(carbon copy)
- BCC(Blind carbon copy)