ESMTP (Extended Simple Mail Transfer Protocol) specifies extensions to the original protocol for sending e-mail that supports graphics, audio and video files, and text in various national languages. The original Internet protocols for sending e-mail are described in Request for Comments (RFC) 822, Standard for the Format of ARPA Internet Text Messages, and in RFC 821, Simple Mail Transfer Protocol (SMTP). ESMTP provides the capability for a client e-mail program to ask a server e-mail program which capabilities it supports and then communicate accordingly.
