What is the SMTP DATA clause?
The DATA clause is what the sending server uses to indicate that it now wants to send the actual mail message. The message itself consists of all the message headers followed by a blank line followed by the message body and finally a single dot on a line by itself. This single dot on a line by itself (often referred to as CRLF.CRLF) is the end of message indicator, i.e. it terminates the DATA phase of the protocol.
Keywords:RFC821, 821, SMTP, DATA, protocol