Simple Mail Transfer Protocol

Simple Mail Transfer Protocol, also referred to as SMTP, is primarily a text based protocol. In such protocol, a mail writer communicates with a mail receiver by issuing command strings and providing necessary data. These command strings are the precise words that direct a server to perform actions. This data is transmitted through a consistent ordered data stream channel. A typical SMTP session includes commands that are sent by a SMTP sender and also the corresponding responses to these commands made by a SMTP receiver. This facilitates the exchange of session parameters and thereby a session is started. Once the session is established, the sender then transmits the required information to the receiver as per the protocols that regulate the transfer of data packets.

This Internet standard for e-mail transmission was initially defined by RFC 821 in the year 1982 and was finally updated in the year 2008 with the aid of Extended SMTP additions by RFC 5321