See what "E-mail" is in other dictionaries:

Titles

If in Europe, America and other regions, only two spellings are used - "email" and, less often, "e-mail"(since March 2011, English-language media are encouraged to write the abbreviation for “electronic mail” as “email” and not “e-mail”), then there is significant variability in Russian. Most often in Cyrillic texts, “e-mail” is also used, that is, writing in Latin without transliteration (visual perception of other forms of writing is worse). But you can find other spellings:

The correct spelling is not yet recorded in dictionaries. The help desk of Gramota.ru indicates that E. Vaulina in the dictionary "My Computer" suggests writing e-mail And e-mail, but notices that such a spelling does not correspond to the literary norm, at the same time, in another answer, it is advised to write e-mail Latin.

De facto in official Russian-language documents:

• in the text (in the sense of "method of communication") they use the expression "Email";
• prefix is ​​used in contact list "e-mail"(E-mail: [email protected]).

History

The emergence of e-mail can be traced back to 1965, when employees (MIT) Noel Morris and Tom Van Vleck wrote the MAIL program for the CTSS (Compatible Time-Sharing System) operating system installed on an IBM 7090/7094 computer.

The text interface of the mail program

The general development of email has been through the development of local user interaction on multi-user systems. Users could, using the mail program (or its equivalent), forward messages to each other within the same mainframe (large computer). The next step was to be able to forward the message to a user on another machine - this was done by specifying the machine name and the username on the machine. The address could be written in the form foo!joe (user joe on computer foo). The third step in the development of e-mail occurred with the advent of the transmission of letters through a third computer. In the case of using UUCP, the user's address included a route to the user through several intermediate machines (for example, gate1!gate2!foo!joe - a letter for joe through the gate1 machine, gate2 to the foo machine). The disadvantage of this addressing was that the sender (or the administrator of the machine on which the sender was running) needed to know the exact path to the destination machine.

After the advent of the distributed global name system DNS, domain names began to be used to indicate the address - [email protected]- user user on machine example.com. At the same time, the concept of “on a machine” was being rethought: dedicated servers began to be used for mail, to which ordinary users (only administrators) did not have access, and users worked on their machines, while mail did not come to users’ workstations, but to mailboxes. a server from where users retrieved their mail using various network protocols (among the most common at the moment are POP3, IMAP, MAPI, web interfaces). Simultaneously with the advent of DNS, a system for reserving mail delivery routes was thought out, and the domain name in the mailing address ceased to be the name of a specific computer and became just a fragment of the mailing address. Many servers may be responsible for maintaining a domain (perhaps physically located on different continents and in different organizations), and users from the same domain may have nothing in common (this is especially true for users of free email servers).

In addition, there were other e-mail systems (some of which still exist), such as: Netmail on the Fidonet network, X.400 on X.25 networks [ clarify] . Access to them from the Internet and vice versa is carried out through a mail gateway. To route mail in X.25 networks, DNS provides a special resource record with the appropriate name X25 (code 19).

Chronology

• 1996, July 4 (US Independence Day) - the beginning of the commercial operation of the Hotmail mail service. The start date of the service symbolized the release from Internet providers.
• March 8, 1997 - Yahoo! acquires the RocketMail Portal, one of the first free email services. The advent of Yahoo! Mail.
• 1998, October 15 - free e-mail from Mail.Ru was launched.
• 2000, June 26 - Yandex.Mail is launched - a free mail service from Yandex.

Modern Architecture (SMTP)

The most commonly used email exchange protocol in the world is SMTP. simple mail transfer protocol- simple mail transfer protocol). In a common implementation, it uses DNS to determine mail forwarding rules (although in private systems like Microsoft Exchange, SMTP can act on information from other sources).

IMAP

Concept post terminal implies that all correspondence associated with the mailbox (including copies of sent emails) is stored on the server, and the user accesses the repository (sometimes traditionally also called the "mailbox") to view correspondence (both new and archived) and writing new letters (including replies to other letters). The IMAP protocol and most web interfaces of free email services operate on this principle. Such storage of mail correspondence requires significantly more capacity from mail servers, as a result, in many cases there is a separation between mail servers that forward mail and mail storage servers.

Differences

Based on the work of the protocols, they can be divided according to two main criteria:

• Server performance - in this case, IMAP is more demanding on resources than POP3, since all mail processing work (such as searching) falls on the shoulders of the server, POP3 only transfers mail to the client;
• Bandwidth - here IMAP wins; POP3 sends the entire body of all emails, while IMAP only sends the headers of the emails, and the rest is on request.

Under certain conditions, the mail storage server can be configured to behave similarly to the client: such a server accesses the mail server using the POP3 protocol and takes mail for itself. Such solutions are usually used in small organizations that do not have the infrastructure to deploy full-fledged mail servers; in this case, a local server is used to store mail and a provider's mail server that provides the service of receiving mail via POP3 (for example, using fetchmail). The main disadvantage of such a solution is the delay in delivery (since the software that collects mail accesses the servers with some delay) - for example, the POP3 connector from Exchange 2003 Server as part of Windows SBS does not allow setting an interval of less than 15 minutes through the configuration interface.

Letter structure

When transmitting via SMTP email consists of the following parts:

• The SMTP protocol headers received by the server. These headers may or may not be included later in the message, so it is possible that the server has more information about the message than is contained in the message itself. So, for example, the RCPT TO field indicates the recipient of the letter, while the recipient may not be specified in the letter itself. This information is transmitted outside the server only within the SMTP protocol, and a protocol change during mail delivery (for example, at the recipient host during internal routing) can lead to the loss of this information. In most cases, this information is not available to the final recipient who uses non-SMTP protocols (POP3, IMAP) to access the mailbox. To be able to monitor the health of the system, this information is usually stored in the mail server logs.
• The message itself (in the terminology of the SMTP protocol - "DATA"), which, in turn, consists of the following parts, separated by an empty line:
  • headers (English) headers) letters, sometimes called by analogy with paper mail envelope(English) envelope). The header contains service information and marks of the mail servers through which the letter passed, priority marks, an indication of the address and name of the sender and recipient of the letter, the subject of the letter and other information. There is some confusion with the term “envelope”, because, depending on the situation, either the header of the letter or the information that the SMTP server has after receiving the letter is called the “envelope” (for example, in the documentation for the postfix mail server, the term “envelope” used for SMTP data that includes not only the RCPT TO and MAIL FROM fields, but also the sender's IP address, its HELO string, etc.)
  • The body of the letter. In the body of the letter is, in fact, the message of the letter. According to the standard, only 7-bit ASCII characters can be in the body of the letter. Therefore, when using national encodings, various forms of information presentation (HTML, RTF, images, attachment binary files), the body of the message must be encoded according to the MIME standard and cannot be read by a person without using a decoder or an email client with such a decoder.

SMTP header

The SMTP header contains the following information:

• name of the sending host (not the name of the sender, but the name of the server or computer of the user who accessed the server) - a HELO/EHLO message parameter, usually supplemented with "objective" information by the server itself (HELO can contain an arbitrary name, and the sender's IP is much more difficult to fake), the IP address is used to search for a PTR record in DNS, all this together allows you to identify the sender at the network level (and in reality it is often used to check the reliability of the sender using black / white lists, including via the Internet - see RBL).
• MAIL FROM: field containing the sender's address. The address can be arbitrary (including from non-existent domains, however, this address can also be checked during the initial spam check).
• The RCPT TO: field is the most important field for mail delivery, containing the recipient's email address. Most mail systems will check if the user exists if possible and may refuse to accept mail if the user specified in RCPT TO does not exist.

Email header

The email header is described by the RFC standards:

• RFC 2076 - Common Internet Message Headers generally accepted standards for message headers), includes information from other RFCs: RFC 822 , RFC 1036 , RFC 1123 , RFC 1327 , RFC 1496 , RFC 1521 , RFC 1766 , RFC 1806 , RFC 1864 , RFC 1911).
• RFC 4021 - Registration of Mail and MIME Header Fields ( mail logging and MIME header fields).

The header is separated from the body of the letter by an empty line. The header is used to log the passage of the letter and service marks (sometimes the logging and mark lines are called kludges). In Microsoft Outlook, this heading is called "Internet Headers" (it is understood that each line is a separate heading). The header usually indicates: the mail servers through which the letter passed (each mail server adds information about who it received this letter from), information about whether this letter looks like spam, information about antivirus scanning, the level of urgency of the letter (maybe change mail servers). Also in the header is usually written the program with which the letter was created. Most often, email clients hide the headers from the user during normal use of the mail system, but provide the ability to see the headers if there is a need for a more detailed analysis of the letter. If an email from SMTP format is converted to another format (for example, in Microsoft Exchange 2007 emails are converted from SMTP format to MAPI), the headers are stored separately for diagnostic purposes.

Headings are usually added from the bottom up (that is, each time a heading needs to be added to a message, it is added on the first line, before all the previous ones).

In addition to service information, email headers also store information displayed to the user, this is usually the sender of the letter, recipient, subject and date of sending.

Frequently used fields

• Return-Path (RFC 821 , RFC 1123) - return address. May be different from MAIL FROM (that is, the return address may be specified differently from the sender's address).
• Received (RFC 822 , RFC 1123) - line for logging message passing. Each mail server (MTA) marks the processing with this message. If the message passes through several mail servers (the usual situation), then new messages are added above the previous ones (and the transfer log is read in reverse order, from the nearest node to the farthest).
• MIME-Version (RFC 1521) - The MIME version with which this message was created. Since the message is created before all other events with the letter, this header is usually the very first (that is, the last in the list).
• From: (RFC 822 , RFC 1123 , RFC 1036) - Name and address of the sender (it is in this header that the text field with the name of the sender appears). May not match the return-path, and may not even match the SMTP MAIL FROM: header.
• Sender: (RFC 822 , RFC 1123) - The sender of the message. Added to be able to indicate that a letter on behalf of someone (from) was sent by another person (for example, a secretary on behalf of the boss). Some mail clients show the message in the presence of sender and from as "message from 'sender' on behalf of 'from'". Sender is an informational header (and may also be different from the SMTP MAIL FROM header).
• To: (RFC 822 , RFC 1123) - The name and address of the recipient. It can be contained several times (if the letter is addressed to several recipients). Might not match the SMTP RCPT TO field.
• cc: (RFC 822 , RFC 1123) - (from English. carbon copy). Contains the names and addresses of the secondary recipients of the letter to whom the copy is sent.
• bcc: (RFC 822 , RFC 1123) - (from English. blind carbon copy). Contains the names and addresses of email recipients whose addresses should not be shown to other recipients. This field is usually handled by the mail server (and results in several different messages where the bcc contains only the recipient the email is actually addressed to). Each of the recipients will not see other recipients from the bcc field in this field.
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