Smtp

Simple Mail Transfer Protocol (smtp) is the protocol standard for the transmission via email Internet . In Italian it could be translate like "elementary Protocol of transfer mails them".

It is a relatively simple, testuale protocol, in which they come specifies or more adressees to you than a message, verified their existence, the message comes transferred. It is enough easy to verify like works a serveur smtp by means of client a telnet. The smtp uses the protocol of transmission TCP and, in order to approach to you, door 25. In order to associate serveur smtp to a data name of dominion (DNS) a called record MX (Mail Exchange is used).

The smtp began to diffuse itself in first years ' 80. To that time it was an alternative tothe UUCP, that more it was adapted to manage the transfer of email between computer whose logon was intermittent. The smtp, of other part, works better if the computers are always connect you to the net.

Sendmail was one of first (if not just the first) mail transfer agent to implement protocol smtp. Until the 2001 they have been at least written 50 programs that implement protocol smtp like client (sender of the messages) or serveur (adressee of the message). Other serveur much diffuse is Exim di Philip Hazel, Postfix di Wietse Venema, qmail of D. J. Bernstein, Courier di Sam Varshavchik and Microsoft Exchange Serveur.

Since smtp is a testuale protocol based on codifies ASCII, it is not allowed to directly transmit to text composed with a various character set and tantomeno binary rows. Standard MIME allows to extend the format of the messages maintaining the compatibility with the existing software. As an example, to the day today much serveur smtp supports extension 8BITMIME, which allows a transfer of a text that contains accented characters (non-ASCII) without need of trascodificarlo. Other limits of smtp, which the maximum length of a line, prevents the shipment of binary rows without trascodifica. (Famous that for the binary rows it sendes to you with HTTP it uses format MIME without need of one trascodifica.)

The smtp is a protocol that only allows to send mail messages, but not to demand them to a serveur: in order to make this the client of mail it must use other protocols, which the POP3, or Post Office Protocol,the IMAP, or Internet Message Access Protocol.