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| | E-mail is an abbreviation of electronic mail - name of technology & service rendered for transferring and receiving electronic messages (called “mails) along distributed (including global) computer network. Basic difference from other message transfer systems (for example, instant messaging services) differs by possibility of postponed delivery, developed (and confused due to prolonged development) interaction system between independent mail servers.
History:
Appearance of email can be dated to 1965, when employees of Massachusetts Institute of Technology (MIT) Noel Morris and Tom Van Vleck have written program MAIL for operating system CTSS (Compatible Time-Sharing System), installed on computer IBM 7090/7094.
After appearance of distributed global system by the name DNS, domain names - user@example.com - user on machine example.com were used for indicating the address. Simultaneously, reviewing the concepts “on machine” occurred: Dedicated server was used for mails and the regular did not have access to the servers (only administrators had access) and users worked on their computer; in this case, mails were received by the server but not the working computers of users & users received their mails through various network protocols from server (among widely used at present - POP3, IMAP, RCP, web interfaces). Simultaneously with the advent of DNS, reservation system for operating the mail servers was invented & domain name in mail address has ceased to be name of concrete computer & simply became mail domain, maintenance of which was looked after by many servers (probably, physically located on different continents & in different organizations).
Besides, even other e-mail systems existed (some of them exist even now) such as Netmail in network FidoNET, X.400 in networks X.25. Access to them through Internet & back was accomplished through mail gateway.
Modern architecture:
If mail transfer issues through UUCP are not touched upon, then the modern architecture of mail servers interaction looks like the following: mail systems, independent of each other, are fixed in various domains. Each mail domain can have several users. (However, actually, one organization or an individual can own many domains, which are served (physically) by single mail system). Mail is transferred between units with the use of Mail Transfer Agent programs (such as, for example, sendmail, exim4, postfix, Microsoft Exchange Server, Lotus Domino etc.). Behavior of systems while communicating with each other is strictly standardized, for this protocol SMTP is used (and observance of this standard, on level with public support DNS by all participants is foundation for possibility of communication “from all with all” without preliminary arrangements). Communication of mail system & users, generally, is not regulated in any way & can be arbitrary, even though exist both open as well as close (connected with software of concrete manufacturers) protocols for communication between the users & mail system. Program, working in mail system & serving the users, is called MDA (Mail Delivery Agent). In some mail systems, MDA & MTA can be combined into single program; MDA & MTA can be diversified in the form of different programs in other systems or generally executed on various servers. Program, with the help of which, user gains access is called MUA (Mail User Agent), though, in case, for example, web-interface can even be absent.
Several mail servers, executing both forwarding of mail within the organization as well as other tasks, linked with e-mail can be provided within the given mail system (usually present within a single organization). The other tasks are spam filtration, checking the contents with antivirus, auto reply provision, archiving incoming & outgoing mails, providing access to users through various methods (from POP3 to ActiveSync). Communication between servers within the limits of single mail system can be slave to general rules (use of DNS & mail routing rules with the help of SMTP), as well as follow own rules of the company (using software).
Relays:
DNS allows in specifying any unit of internet, not necessarily the part of domain zone of addressee’s domain as accepting server (MX-entry). It can be used for adjusting relaying (transfers) of mails through third server. Foreign server (for example, more reliable than user’s server) receives the mails for user’s domain & delivers them to mailing servers of user as soon as possibility appears. Historically, control over “send mail to whom” was not available (or due importance was not given) & servers transferred mails to any domains without similar monitoring. Such servers are called “Open Relays” (presently, new open relays are appearing mainly due to the mistakes in server configuration). |
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Shocking news today - hackers broke into the Yahoo! e-mail account of Sarah Palin and sent screenshots of her email correspondence to several major blog websites and even Associated Press.
Hackers claim that Palin used Yahoo email, instead of her official Alaska governor email, to hide a lot of her correspondence which she never wished to become public, including emails linked to her records, which she refused to make public. The Secret Service approached The Associated Press requesting the copies of Palin's emails which The AP received from hackers. The AP refused to comply. McCain-Palin camp is furious and demand the full investigation and prosecution of hackers calling this a "shocking invasion of the governor's privacy and a violation of law".
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