SMTP Status Codes

Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmissions across the Internet. Formally SMTP is defined in RFC 821 as amended by RFC 1123. The protocol used today is also known as ESMTP and defined in RFC 2821. The main role of this article is not to explain SMTP as itself (RFC’s describe this pretty deeply) but provide quick reference to SMTP Reply Codes. An example of basic SMTP communication is also stated here, below table.
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