Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other electrically charged particles . It is a subfield of physics and electrical engineering which uses active devices such as transistors , diodes , and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog signals to digital signals.
96-599: Email (short for electronic mail ; alternatively spelled e-mail ) is a method of transmitting and receiving messages using electronic devices. It was conceived in the late–20th century as the digital version of, or counterpart to, mail (hence e- + mail ). Email is a ubiquitous and very widely used communication medium; in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries. Email operates across computer networks , primarily
192-432: A mass-production basis, which limited them to a number of specialised applications. The MOSFET was invented at Bell Labs between 1955 and 1960. It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses. Its advantages include high scalability , affordability, low power consumption, and high density . It revolutionized the electronics industry , becoming
288-413: A name-addr , which contains a display-name and addr-spec , or the more common addr-spec alone. An email address, such as john.smith@example.com , is made up from a local-part , the symbol @, and a domain , which may be a domain name or an IP address enclosed in brackets. Although the standard requires the local-part to be case-sensitive, it also urges that receiving hosts deliver messages in
384-446: A case-independent manner, e.g., that the mail system in the domain example.com treat John.Smith as equivalent to john.smith ; some mail systems even treat them as equivalent to johnsmith . Mail systems often limit the users' choice of name to a subset of the technically permitted characters; with the introduction of internationalized domain names , efforts are progressing to permit non- ASCII characters in email addresses. Due to
480-557: A current Internet connection. The Post Office Protocol 3 (POP3) is a mail access protocol used by a client application to read messages from the mail server. Received messages are often deleted from the server . POP supports simple download-and-delete requirements for access to remote mailboxes (termed maildrop in the POP RFC's). POP3 allows downloading messages on a local computer and reading them even when offline. The Internet Message Access Protocol (IMAP) provides features to manage
576-412: A few characters outside that range and base64 for arbitrary binary data. The 8BITMIME and BINARY extensions were introduced to allow transmission of mail without the need for these encodings, but many mail transport agents may not support them. In some countries, e-mail software violates RFC 5322 by sending raw non-ASCII text and several encoding schemes co-exist; as a result, by default,
672-565: A file by email. Where larger files need to be shared, various file hosting services are available and commonly used. Electronics Electronic devices have hugely influenced the development of many aspects of modern society, such as telecommunications , entertainment, education, health care, industry, and security. The main driving force behind the advancement of electronics is the semiconductor industry , which in response to global demand continually produces ever-more sophisticated electronic devices and circuits. The semiconductor industry
768-437: A large corporate environment, with a proprietary protocol specific to Novell Groupwise , Lotus Notes or Microsoft Exchange Servers . Programs used by users for retrieving, reading, and managing email are called mail user agents (MUAs). When opening an email, it is marked as "read", which typically visibly distinguishes it from "unread" messages on clients' user interfaces. Email clients may allow hiding read emails from
864-508: A local-part (sometimes a user name, but not always) and a domain; if the domain is a domain name rather than an IP address then the SMTP client uses the domain name to look up the mail exchange IP address. The general format of an email address is local-part @ domain , e.g. jsmith@[192.168.1.2], jsmith@example.com . The SMTP client transmits the message to the mail exchange, which may forward it to another mail exchange until it eventually arrives at
960-811: A local-part as well as a domain name. Comments are allowed in the domain as well as in the local-part; for example, john.smith@(comment)example.com and john.smith@example.com(comment) are equivalent to john.smith@example.com . RFC 2606 specifies that certain domains, for example those intended for documentation and testing, should not be resolvable and that as a result mail addressed to mailboxes in them and their subdomains should be non-deliverable. Of note for e-mail are example , invalid , example.com , example.net , and example.org . Email addresses are often requested as input to website as validation of user existence. Other validation methods are available, such as cell phone number validation, postal mail validation, and fax validation. An email address
1056-409: A mail store by programs called mail delivery agents (MDAs, also sometimes called local delivery agents, LDAs). Accepting a message obliges an MTA to deliver it, and when a message cannot be delivered, that MTA must send a bounce message back to the sender, indicating the problem. Users can retrieve their messages from servers using standard protocols such as POP or IMAP , or, as is more likely in
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#17327824799471152-402: A mailbox from multiple devices. Small portable devices like smartphones are increasingly used to check email while traveling and to make brief replies, larger devices with better keyboard access being used to reply at greater length. IMAP shows the headers of messages, the sender and the subject and the device needs to request to download specific messages. Usually, the mail is left in folders in
1248-566: A mix of the two types. Analog circuits are becoming less common, as many of their functions are being digitized. Analog circuits use a continuous range of voltage or current for signal processing, as opposed to the discrete levels used in digital circuits. Analog circuits were common throughout an electronic device in the early years in devices such as radio receivers and transmitters. Analog electronic computers were valuable for solving problems with continuous variables until digital processing advanced. As semiconductor technology developed, many of
1344-420: A notable implementation by MIT 's CTSS project in 1965. Most developers of early mainframes and minicomputers developed similar, but generally incompatible, mail applications. In 1971 the first ARPANET network mail was sent, introducing the now-familiar address syntax with the ' @ ' symbol designating the user's system address. Over a series of RFCs , conventions were refined for sending mail messages over
1440-540: A physical space, although in more recent years the trend has been towards electronics lab simulation software , such as CircuitLogix , Multisim , and PSpice . Today's electronics engineers have the ability to design circuits using premanufactured building blocks such as power supplies , semiconductors (i.e. semiconductor devices, such as transistors), and integrated circuits. Electronic design automation software programs include schematic capture programs and printed circuit board design programs. Popular names in
1536-403: A quoted-pair consisting of a Backslash followed by HT, Space or any ASCII graphic; it may also be split between lines anywhere that HT or Space appears. In contrast to unquoted local-parts, the addresses ".John.Doe"@example.com , "John.Doe."@example.com and "John..Doe"@example.com are allowed. The maximum total length of the local-part of an email address is 64 octets. In addition to
1632-427: A single email address may be the alias to a distribution list to many mailboxes. Email aliases , electronic mailing lists , sub-addressing , and catch-all addresses, the latter being mailboxes that receive messages regardless of the local-part, are common patterns for achieving a variety of delivery goals. The addresses found in the header fields of an email message are not directly used by mail exchanges to deliver
1728-409: A single piece of electronic mail is called a message . The conventions for fields within emails—the "To", "From", "CC", "BCC" etc.—began with RFC-680 in 1975. An Internet email consists of an envelope and content ; the content consists of a header and a body . Computer-based messaging between users of the same system became possible after the advent of time-sharing in the early 1960s, with
1824-711: A smartphone ranges and differs dramatically across different countries. For example, in comparison to 75% of those consumers in the US who used it, only 17% in India did. As of 2010, the number of Americans visiting email web sites had fallen 6 percent after peaking in November 2009. For persons 12 to 17, the number was down 18 percent. Young people preferred instant messaging , texting and social media . Technology writer Matt Richtel said in The New York Times that email
1920-576: A variety of formats for addressing, today, email addresses follow a set of specific rules originally standardized by the Internet Engineering Task Force (IETF) in the 1980s, and updated by RFC 5322 and 6854 . The term email address in this article refers to just the addr-spec in Section 3.4 of RFC 5322 . The RFC defines address more broadly as either a mailbox or group . A mailbox value can be either
2016-482: Is local-part@domain , where the local-part may be up to 64 octets long and the domain may have a maximum of 255 octets. The formal definitions are in RFC 5322 (sections 3.2.3 and 3.4.1) and RFC 5321—with a more readable form given in the informational RFC 3696 (written by J. Klensin, the author of RFC 5321 ) and the associated errata. An email address also may have an associated "display-name" (Display Name) for
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#17327824799472112-790: Is also known as plus addressing , tagged addressing or mail extensions . This can be useful for tagging emails for sorting, and for spam control. Addresses of this form, using various separators between the base name and the tag, are supported by several email services, including Andrew Project (plus), Runbox (plus), Gmail (plus), Rackspace (plus), Yahoo! Mail Plus (hyphen), Apple's iCloud (plus), Outlook.com (plus), Mailfence (plus), Proton Mail (plus), Fastmail (plus and Subdomain Addressing), postale.io (plus), Pobox (plus), MeMail (plus), and MTAs like MMDF (equals), Qmail and Courier Mail Server (hyphen). Postfix and Exim allow configuring an arbitrary separator from
2208-585: Is also part of the header, as defined below. SMTP defines the trace information of a message saved in the header using the following two fields: Other fields added on top of the header by the receiving server may be called trace fields . Internet email was designed for 7-bit ASCII. Most email software is 8-bit clean , but must assume it will communicate with 7-bit servers and mail readers. The MIME standard introduced character set specifiers and two content transfer encodings to enable transmission of non-ASCII data: quoted printable for mostly 7-bit content with
2304-548: Is defined as unwanted disturbances superposed on a useful signal that tend to obscure its information content. Noise is not the same as signal distortion caused by a circuit. Noise is associated with all electronic circuits. Noise may be electromagnetically or thermally generated, which can be decreased by lowering the operating temperature of the circuit. Other types of noise, such as shot noise cannot be removed as they are due to limitations in physical properties. Many different methods of connecting components have been used over
2400-515: Is defined by RFC 5322 , with encoding of non-ASCII data and multimedia content attachments defined in RFC 2045 through RFC 2049, collectively called Multipurpose Internet Mail Extensions or MIME . The extensions in International email apply only to email. RFC 5322 replaced RFC 2822 in 2008. Earlier, in 2001, RFC 2822 had in turn replaced RFC 822, which had been the standard for Internet email for decades. Published in 1982, RFC 822
2496-478: Is expected in China, Japan, Russia, and other markets that have large user bases in a non-Latin-based writing system. For example, in addition to the .in top-level domain, the government of India in 2011 got approval for ".bharat", (from Bhārat Gaṇarājya ), written in seven different scripts for use by Gujrati, Marathi, Bangali, Tamil, Telugu, Punjabi and Urdu speakers. Indian company XgenPlus.com claims to be
2592-470: Is generally recognized as having two parts joined with an at-sign ( @ ), although technical specification detailed in RFC 822 and subsequent RFCs are more extensive. Syntactically correct, verified email addresses do not guarantee that an email box exists. Thus many mail servers use other techniques and check the mailbox existence against relevant systems such as the Domain Name System for
2688-561: Is no guarantee that it will provide accurate results. The IETF conducts a technical and standards working group devoted to internationalization issues of email addresses, entitled Email Address Internationalization (EAI, also known as IMA, Internationalized Mail Address). This group produced RFC 6530 , 6531 , 6532 and 6533 , and continues to work on additional EAI-related RFCs. The IETF's EAI Working group published RFC 6530 "Overview and Framework for Internationalized Email", which enabled non-ASCII characters to be used in both
2784-455: Is no technical restriction on the size or number of attachments. However, in practice, email clients, servers , and Internet service providers implement various limitations on the size of files, or complete email – typically to 25MB or less. Furthermore, due to technical reasons, attachment sizes as seen by these transport systems can differ from what the user sees, which can be confusing to senders when trying to assess whether they can safely send
2880-492: Is often successfully used to send special sales offerings and new product information. Depending on the recipient's culture, email sent without permission—such as an "opt-in"—is likely to be viewed as unwelcome " email spam ". Many users access their personal emails from friends and family members using a personal computer in their house or apartment. Email has become used on smartphones and on all types of computers. Mobile "apps" for email increase accessibility to
2976-421: Is one of the largest and most profitable sectors in the global economy, with annual revenues exceeding $ 481 billion in 2018. The electronics industry also encompasses other sectors that rely on electronic devices and systems, such as e-commerce, which generated over $ 29 trillion in online sales in 2017. The identification of the electron in 1897 by Sir Joseph John Thomson , along with the subsequent invention of
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3072-419: Is supplied separately to the transport protocol, SMTP , which may be extracted from the header content. The "To:" field is similar to the addressing at the top of a conventional letter delivered according to the address on the outer envelope. In the same way, the "From:" field may not be the sender. Some mail servers apply email authentication systems to messages relayed. Data pertaining to the server's activity
3168-595: Is the voltage comparator which receives a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch , having essentially two levels of output. Analog circuits are still widely used for signal amplification, such as in the entertainment industry, and conditioning signals from analog sensors, such as in industrial measurement and control. Digital circuits are electric circuits based on discrete voltage levels. Digital circuits use Boolean algebra and are
3264-448: Is therefore the process of defining and developing complex electronic devices to satisfy specified requirements of the user. Due to the complex nature of electronics theory, laboratory experimentation is an important part of the development of electronic devices. These experiments are used to test or verify the engineer's design and detect errors. Historically, electronics labs have consisted of electronics devices and equipment located in
3360-482: The File Transfer Protocol . Proprietary electronic mail systems soon began to emerge. IBM , CompuServe and Xerox used in-house mail systems in the 1970s; CompuServe sold a commercial intraoffice mail product in 1978 to IBM and to Xerox from 1981. DEC's ALL-IN-1 and Hewlett-Packard's HPMAIL (later HP DeskManager) were released in 1982; development work on the former began in the late 1970s and
3456-624: The IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. The 608 contained more than 3,000 germanium transistors. Thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic circuits and peripheral devices. However, early junction transistors were relatively bulky devices that were difficult to manufacture on
3552-499: The Internet , and also local area networks . Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need to connect, typically to a mail server or a webmail interface to send or receive messages or download it. Originally a text-only ASCII communications medium, Internet email
3648-552: The LDH rule (letters, digits, hyphen). In addition, the domain may be an IP address literal, surrounded by square brackets [] , such as jsmith@[192.168.2.1] or jsmith@[IPv6:2001:db8::1] , although this is rarely seen except in email spam . Internationalized domain names (which are encoded to comply with the requirements for a hostname ) allow for presentation of non-ASCII domains. In mail systems compliant with RFC 6531 and RFC 6532 an email address may be encoded as UTF-8 , both
3744-695: The SMTP protocol and either the Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP). When transmitting email messages , mail user agents (MUAs) and mail transfer agents (MTAs) use the domain name system (DNS) to look up a Resource Record (RR) for the recipient's domain. A mail exchanger resource record ( MX record ) contains the name of the recipient's mailserver. In absence of an MX record, an address record ( A or AAAA ) directly specifies
3840-441: The vacuum tube which could amplify and rectify small electrical signals , inaugurated the field of electronics and the electron age. Practical applications started with the invention of the diode by Ambrose Fleming and the triode by Lee De Forest in the early 1900s, which made the detection of small electrical voltages, such as radio signals from a radio antenna , practicable. Vacuum tubes (thermionic valves) were
3936-448: The 1960s, U.S. manufacturers were unable to compete with Japanese companies such as Sony and Hitachi who could produce high-quality goods at lower prices. By the 1980s, however, U.S. manufacturers became the world leaders in semiconductor development and assembly. However, during the 1990s and subsequently, the industry shifted overwhelmingly to East Asia (a process begun with the initial movement of microchip mass-production there in
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4032-538: The 1970s), as plentiful, cheap labor, and increasing technological sophistication, became widely available there. Over three decades, the United States' global share of semiconductor manufacturing capacity fell, from 37% in 1990, to 12% in 2022. America's pre-eminent semiconductor manufacturer, Intel Corporation , fell far behind its subcontractor Taiwan Semiconductor Manufacturing Company (TSMC) in manufacturing technology. By that time, Taiwan had become
4128-712: The EDA software world are NI Multisim, Cadence ( ORCAD ), EAGLE PCB and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium (Protel), LabCentre Electronics (Proteus), gEDA , KiCad and many others. Heat generated by electronic circuitry must be dissipated to prevent immediate failure and improve long term reliability. Heat dissipation is mostly achieved by passive conduction/convection. Means to achieve greater dissipation include heat sinks and fans for air cooling, and other forms of computer cooling such as water cooling . These techniques use convection , conduction , and radiation of heat energy . Electronic noise
4224-788: The Internet included other notations, such as that required by X.400 , and the UUCP bang path notation, in which the address was given in the form of a sequence of computers through which the message should be relayed. This was widely used for several years, but was superseded by the Internet standards promulgated by the Internet Engineering Task Force (IETF). The local-part of the email address may be unquoted or may be enclosed in quotation marks. If unquoted, it may use any of these ASCII characters: If quoted, it may contain Space, Horizontal Tab (HT), any ASCII graphic except Backslash and Quote and
4320-489: The Local-part is case-sensitive". Despite the wide range of special characters which are technically valid, organisations, mail services, mail servers and mail clients in practice often do not accept all of them. For example, Windows Live Hotmail only allows creation of email addresses using alphanumerics, dot ( . ), underscore ( _ ) and hyphen ( - ). Common advice is to avoid using some special characters to avoid
4416-586: The Local-part requires (or uses) the Quoted-string form". The local-part postmaster is treated specially—it is case-insensitive, and should be forwarded to the domain email administrator. Technically all other local-parts are case-sensitive, therefore johns@example.com and JohnS@example.com specify different mailboxes; however, many organizations treat uppercase and lowercase letters as equivalent. Indeed, RFC 5321 warns that "a host that expects to receive mail SHOULD avoid defining mailboxes where ...
4512-507: The URL in the To: field. Many clients also support query string parameters for the other email fields, such as its subject line or carbon copy recipients. Many email providers have a web-based email client. This allows users to log into the email account by using any compatible web browser to send and receive their email. Mail is typically not downloaded to the web client, so it cannot be read without
4608-430: The ability to be used for more frequent communication between users and allowed them to check their email and write messages throughout the day. As of 2011, there were approximately 1.4 billion email users worldwide and 50 billion non-spam emails that were sent daily. Individuals often check emails on smartphones for both personal and work-related messages. It was found that US adults check their email more than they browse
4704-416: The ability to include in-line links and images, set apart previous messages in block quotes , wrap naturally on any display, use emphasis such as underlines and italics , and change font styles. Disadvantages include the increased size of the email, privacy concerns about web bugs , abuse of HTML email as a vector for phishing attacks and the spread of malicious software . Some e-mail clients interpret
4800-575: The above ASCII characters, international characters above U+007F, encoded as UTF-8 , are permitted by RFC 6531 when the EHLO specifies SMTPUTF8 , though even mail systems that support SMTPUTF8 and 8BITMIME may restrict which characters to use when assigning local-parts. A local-part is either a Dot-string or a Quoted-string; it cannot be a combination. Quoted strings and characters, however, are not commonly used. RFC 5321 also warns that "a host that expects to receive mail SHOULD avoid defining mailboxes where
4896-451: The attachments. Others separate attachments from messages and save them in a specific directory. The URI scheme , as registered with the IANA, defines the mailto: scheme for SMTP email addresses. Though its use is not strictly defined, URLs of this form are intended to be used to open the new message window of the user's mail client when the URL is activated, with the address as defined by
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#17327824799474992-409: The basis of all digital computers and microprocessor devices. They range from simple logic gates to large integrated circuits, employing millions of such gates. Digital circuits use a binary system with two voltage levels labelled "0" and "1" to indicated logical status. Often logic "0" will be a lower voltage and referred to as "Low" while logic "1" is referred to as "High". However, some systems use
5088-464: The body as HTML even in the absence of a Content-Type: html header field; this may cause various problems. Some web-based mailing lists recommend all posts be made in plain text, with 72 or 80 characters per line for all the above reasons, and because they have a significant number of readers using text-based email clients such as Mutt . Various informal conventions evolved for marking up plain text in email and usenet posts, which later led to
5184-459: The circuit, thus slowing the computer. The invention of the integrated circuit by Jack Kilby and Robert Noyce solved this problem by making all the components and the chip out of the same block (monolith) of semiconductor material. The circuits could be made smaller, and the manufacturing process could be automated. This led to the idea of integrating all components on a single-crystal silicon wafer, which led to small-scale integration (SSI) in
5280-399: The conventions and policies implemented in the mail server. For example, case sensitivity may distinguish mailboxes differing only in capitalization of characters of the local-part, although this is not very common. For example, Gmail ignores all dots in the local-part of a @gmail.com address for the purposes of determining account identity. Some mail services support a tag included in
5376-440: The developed world, and it is one of the key parts of an 'e-revolution' in workplace communication (with the other key plank being widespread adoption of highspeed Internet ). A sponsored 2010 study on workplace communication found 83% of U.S. knowledge workers felt email was critical to their success and productivity at work. It has some key benefits to business and other organizations, including: Email marketing via " opt-in "
5472-571: The development of formal languages like setext (c. 1992) and many others , the most popular of them being markdown . Some Microsoft email clients may allow rich formatting using their proprietary Rich Text Format (RTF), but this should be avoided unless the recipient is guaranteed to have a compatible email client. Messages are exchanged between hosts using the Simple Mail Transfer Protocol with software programs called mail transfer agents (MTAs); and delivered to
5568-475: The domain or using callback verification to check if the mailbox exists. Callback verification is an imperfect solution, as it may be disabled to avoid a directory harvest attack , or callbacks may be reported as spam and lead to listing on a DNSBL . Several validation techniques may be utilized to validate a user email address. For example, Some companies offer services to validate an email address, often using an application programming interface , but there
5664-874: The early 1960s, and then medium-scale integration (MSI) in the late 1960s, followed by VLSI . In 2008, billion-transistor processors became commercially available. An electronic component is any component in an electronic system either active or passive. Components are connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits . Passive electronic components are capacitors , inductors , resistors , whilst active components are such as semiconductor devices; transistors and thyristors , which control current flow at electron level. Electronic circuit functions can be divided into two function groups: analog and digital. A particular device may consist of circuitry that has either or
5760-452: The electronic logic gates to generate binary states. Highly integrated devices: Electronic systems design deals with the multi-disciplinary design issues of complex electronic devices and systems, such as mobile phones and computers . The subject covers a broad spectrum, from the design and development of an electronic system ( new product development ) to assuring its proper function, service life and disposal . Electronic systems design
5856-525: The email system: Many MTAs used to accept messages for any recipient on the Internet and do their best to deliver them. Such MTAs are called open mail relays . This was very important in the early days of the Internet when network connections were unreliable. However, this mechanism proved to be exploitable by originators of unsolicited bulk email and as a consequence open mail relays have become rare, and many MTAs do not accept messages from open mail relays. The basic Internet message format used for email
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#17327824799475952-421: The file system. Some clients save individual messages as separate files, while others use various database formats, often proprietary, for collective storage. A historical standard of storage is the mbox format. The specific format used is often indicated by special filename extensions : Some applications (like Apple Mail ) leave attachments encoded in messages for searching while also saving separate copies of
6048-481: The final restrictions on carrying commercial traffic over the Internet ended in 1995, a combination of factors made the current Internet suite of SMTP, POP3 and IMAP email protocols the standard (see Protocol Wars ). The following is a typical sequence of events that takes place when sender Alice transmits a message using a mail user agent (MUA) addressed to the email address of the recipient. In addition to this example, alternatives and complications exist in
6144-544: The first active electronic components which controlled current flow by influencing the flow of individual electrons , and enabled the construction of equipment that used current amplification and rectification to give us radio , television , radar , long-distance telephony and much more. The early growth of electronics was rapid, and by the 1920s, commercial radio broadcasting and telecommunications were becoming widespread and electronic amplifiers were being used in such diverse applications as long-distance telephony and
6240-451: The following fields: RFC 3864 describes registration procedures for message header fields at the IANA ; it provides for permanent and provisional field names, including also fields defined for MIME, netnews, and HTTP, and referencing relevant RFCs. Common header fields for email include: The To: field may be unrelated to the addresses to which the message is delivered. The delivery list
6336-562: The following ways: The electronics industry consists of various sectors. The central driving force behind the entire electronics industry is the semiconductor industry sector, which has annual sales of over $ 481 billion as of 2018. The largest industry sector is e-commerce , which generated over $ 29 trillion in 2017. The most widely manufactured electronic device is the metal-oxide-semiconductor field-effect transistor (MOSFET), with an estimated 13 sextillion MOSFETs having been manufactured between 1960 and 2018. In
6432-489: The functions of analog circuits were taken over by digital circuits, and modern circuits that are entirely analog are less common; their functions being replaced by hybrid approach which, for instance, uses analog circuits at the front end of a device receiving an analog signal, and then use digital processing using microprocessor techniques thereafter. Sometimes it may be difficult to classify some circuits that have elements of both linear and non-linear operation. An example
6528-449: The host of the recipient's mail system. The transmission of electronic mail from the author's computer and between mail hosts in the Internet uses the Simple Mail Transfer Protocol (SMTP), defined in RFC 5321 and 5322 , and extensions such as RFC 6531 . The mailboxes may be accessed and managed by applications on personal computers, mobile devices or webmail sites, using
6624-508: The inbox so the user can focus on the unread. Mail can be stored on the client , on the server side, or in both places. Standard formats for mailboxes include Maildir and mbox . Several prominent email clients use their own proprietary format and require conversion software to transfer email between them. Server-side storage is often in a proprietary format but since access is through a standard protocol such as IMAP, moving email from one server to another can be done with any MUA supporting
6720-592: The latter became the world's largest selling email system. The Simple Mail Transfer Protocol (SMTP) was implemented on the ARPANET in 1983. LAN email systems emerged in the mid-1980s. For a time in the late 1980s and early 1990s, it seemed likely that either a proprietary commercial system or the X.400 email system, part of the Government Open Systems Interconnection Profile (GOSIP), would predominate. However, once
6816-410: The legal character set. The text of the tag may be used to apply filtering, or to create single-use , or disposable email addresses . The domain name part of an email address has to conform to strict guidelines: it must match the requirements for a hostname , a list of dot-separated DNS labels, each label being limited to a length of 63 characters and consisting of: This rule is known as
6912-655: The limit is 998 characters. Header fields defined by RFC 5322 contain only US-ASCII characters; for encoding characters in other sets, a syntax specified in RFC 2047 may be used. In some examples, the IETF EAI working group defines some standards track extensions, replacing previous experimental extensions so UTF-8 encoded Unicode characters may be used within the header. In particular, this allows email addresses to use non-ASCII characters. Such addresses are supported by Google and Microsoft products, and promoted by some government agents. The message header must include at least
7008-720: The local-part of the address, whereas the domain would be restricted by the rules of internationalized domain names , though still transmitted in UTF-8. The mail server is also responsible for any mapping mechanism between the IMA form and any ASCII alias. EAI enables users to have a localized address in a native language script or character set, as well as an ASCII form for communicating with legacy systems or for script-independent use. Applications that recognize internationalized domain names and mail addresses must have facilities to convert these representations. Significant demand for such addresses
7104-467: The local-part, such that the address is an alias to a prefix of the local-part. Typically the characters following a plus and less often the characters following a minus, so fred+bah@domain and fred+foo@domain might end up in the same inbox as fred+@domain or even as fred@domain. For example, the address joeuser+tag@example.com denotes the same delivery address as joeuser@example.com . RFC 5233 refers to this convention as subaddressing , but it
7200-567: The local-parts and domain of an email address. RFC 6530 provides for email based on the UTF-8 encoding, which permits the full repertoire of Unicode . RFC 6531 provides a mechanism for SMTP servers to negotiate transmission of the SMTPUTF8 content. The basic EAI concepts involve exchanging mail in UTF-8. Though the original proposal included a downgrading mechanism for legacy systems, this has now been dropped. The local servers are responsible for
7296-404: The mail host. The local-part of an email address has no significance for intermediate mail relay systems other than the final mailbox host. Email senders and intermediate relay systems must not assume it to be case-insensitive, since the final mailbox host may or may not treat it as such. A single mailbox may receive mail for multiple email addresses, if configured by the administrator. Conversely,
7392-515: The mail server. Messaging Application Programming Interface (MAPI) is used by Microsoft Outlook to communicate to Microsoft Exchange Server —and to a range of other email server products such as Axigen Mail Server , Kerio Connect , Scalix , Zimbra , HP OpenMail , IBM Lotus Notes , Zarafa , and Bynari where vendors have added MAPI support to allow their products to be accessed directly via Outlook. Email has been widely accepted by businesses, governments and non-governmental organizations in
7488-402: The medium for users who are out of their homes. While in the earliest years of email, users could only access email on desktop computers, in the 2010s, it is possible for users to check their email when they are away from home, whether they are across town or across the world. Alerts can also be sent to the smartphone or other devices to notify them immediately of new messages. This has given email
7584-509: The message in a non-Latin alphabet language appears in non-readable form (the only exception is a coincidence if the sender and receiver use the same encoding scheme). Therefore, for international character sets , Unicode is growing in popularity. Most modern graphic email clients allow the use of either plain text or HTML for the message body at the option of the user. HTML email messages often include an automatic-generated plain text copy for compatibility. Advantages of HTML include
7680-426: The message, as unstructured text, sometimes containing a signature block at the end. The header is separated from the body by a blank line. RFC 5322 specifies the syntax of the email header. Each email message has a header (the "header section" of the message, according to the specification), comprising a number of fields ("header fields"). Each field has a name ("field name" or "header field name"), followed by
7776-439: The message. An email message also contains a message envelope that contains the information for mail routing. While envelope and header addresses may be equal, forged email addresses (also called spoofed email addresses ) are often seen in spam , phishing , and many other Internet-based scams. This has led to several initiatives which aim to make such forgeries of fraudulent emails easier to spot. The format of an email address
7872-399: The most widely used electronic device in the world. The MOSFET is the basic element in most modern electronic equipment. As the complexity of circuits grew, problems arose. One problem was the size of the circuit. A complex circuit like a computer was dependent on speed. If the components were large, the wires interconnecting them must be long. The electric signals took time to go through
7968-677: The music recording industry. The next big technological step took several decades to appear, when the first working point-contact transistor was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947. However, vacuum tubes played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since then, solid-state devices have all but completely taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers , cathode-ray tubes , specialist audio equipment, guitar amplifiers and some microwave devices . In April 1955,
8064-449: The protocol. Many current email users do not run MTA, MDA or MUA programs themselves, but use a web-based email platform, such as Gmail or Yahoo! Mail , that performs the same tasks. Such webmail interfaces allow users to access their mail with any standard web browser , from any computer, rather than relying on a local email client. Upon reception of email messages, email client applications save messages in operating system files in
8160-463: The recipient, which precedes the address specification, now surrounded by angled brackets, for example: John Smith <john.smith@example.org> . Email spammers and phishers will often use "Display Name spoofing" to trick their victims, by using a false Display Name, or by using a different email address as the Display Name. Earlier forms of email addresses for other networks than
8256-540: The reverse definition ("0" is "High") or are current based. Quite often the logic designer may reverse these definitions from one circuit to the next as they see fit to facilitate their design. The definition of the levels as "0" or "1" is arbitrary. Ternary (with three states) logic has been studied, and some prototype computers made, but have not gained any significant practical acceptance. Universally, Computers and Digital signal processors are constructed with digital circuits using Transistors such as MOSFETs in
8352-413: The risk of rejected emails. According to RFC 5321 2.3.11 Mailbox and Address, "the local-part MUST be interpreted and assigned semantics only by the host specified in the domain of the address". This means that no assumptions can be made about the meaning of the local-part of another mail server. It is entirely up to the configuration of the mail server. Interpretation of the local-part is dependent on
8448-705: The separator character ":", and a value ("field body" or "header field body"). Each field name begins in the first character of a new line in the header section, and begins with a non- whitespace printable character . It ends with the separator character ":". The separator is followed by the field value (the "field body"). The value can continue onto subsequent lines if those lines have space or tab as their first character. Field names and, without SMTPUTF8 , field bodies are restricted to 7-bit ASCII characters. Some non-ASCII values may be represented using MIME encoded words . Email header fields can be multi-line, with each line recommended to be no more than 78 characters, although
8544-431: The ubiquity of email in today's world, email addresses are often used as regular usernames by many websites and services that provide a user profile or account. For example, if a user wants to login to their Xbox Live video gaming profile, they would use their Microsoft account in the form of an email address as the username ID, even though the service in this case is not email. An email address consists of two parts,
8640-433: The web or check their Facebook accounts, making email the most popular activity for users to do on their smartphones. 78% of the respondents in the study revealed that they check their email on their phone. It was also found that 30% of consumers use only their smartphone to check their email, and 91% were likely to check their email at least once per day on their smartphone. However, the percentage of consumers using email on
8736-458: The world's first EAI mailbox provider, and the Government of Rajasthan now supplies a free email account on domain राजस्थान.भारत for every citizen of the state. A leading media house Rajasthan Patrika launched their IDN domain पत्रिका.भारत with contactable email. The example addresses below would not be handled by RFC 5321 based servers without an extension, but are permitted by
8832-667: The world's leading source of advanced semiconductors —followed by South Korea , the United States , Japan , Singapore , and China . Important semiconductor industry facilities (which often are subsidiaries of a leading producer based elsewhere) also exist in Europe (notably the Netherlands ), Southeast Asia, South America, and Israel . Email address An email address identifies an email box to which messages are delivered. While early messaging systems used
8928-762: The years. For instance, early electronics often used point to point wiring with components attached to wooden breadboards to construct circuits. Cordwood construction and wire wrap were other methods used. Most modern day electronics now use printed circuit boards made of materials such as FR4 , or the cheaper (and less hard-wearing) Synthetic Resin Bonded Paper ( SRBP , also known as Paxoline/Paxolin (trade marks) and FR2) – characterised by its brown colour. Health and environmental concerns associated with electronics assembly have gained increased attention in recent years, especially for products destined to go to European markets. Electrical components are generally mounted in
9024-431: Was based on the earlier RFC 733 for the ARPANET. Internet email messages consist of two sections, "header" and "body". These are known as "content". The header is structured into fields such as From, To, CC, Subject, Date, and other information about the email. In the process of transporting email messages between systems, SMTP communicates delivery parameters and information using message header fields. The body contains
9120-425: Was extended by MIME to carry text in expanded character sets and multimedia content such as images. International email , with internationalized email addresses using UTF-8 , is standardized but not widely adopted. The term electronic mail has been in use with its modern meaning since 1975, and variations of the shorter E-mail have been in use since 1979: The service is often simply referred to as mail , and
9216-551: Was like the VCR , vinyl records and film cameras —no longer cool and something older people do. A 2015 survey of Android users showed that persons 13 to 24 used messaging apps 3.5 times as much as those over 45, and were far less likely to use email. Email messages may have one or more attachments, which are additional files that are appended to the email. Typical attachments include Microsoft Word documents, PDF documents, and scanned images of paper documents. In principle, there
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