"sending".  Because in many hosts the implementation of sending is
      nearly identical to the implementation of mailing these two
      functions are combined in SMTP.  However the sending commands are
      not included in the required minimum implementation
      (Section 4.5.1).  Users should have the ability to control the
      writing of messages on their terminals.  Most hosts permit the
      users to accept or refuse such messages.

      The following three command are defined to support the sending
      options.  These are used in the mail transaction instead of the
      MAIL command and inform the receiver-SMTP of the special semantics
      of this transaction:

         SEND  FROM:<reverse-path> 

            The SEND command requires that the mail data be delivered to
            the user's terminal.  If the user is not active (or not
            accepting terminal messages) on the host a 450 reply may
            returned to a RCPT command.  The mail transaction is
            successful if the message is delivered the terminal.

         SOML  FROM:<reverse-path> 

            The Send Or MaiL command requires that the mail data be
            delivered to the user's terminal if the user is active (and
            accepting terminal messages) on the host.  If the user is
            not active (or not accepting terminal messages) then the
            mail data is entered into the user's mailbox.  The mail
            transaction is successful if the message is delivered either
            to the terminal or the mailbox.

         SAML  FROM:<reverse-path> 

            The Send And MaiL command requires that the mail data be
            delivered to the user's terminal if the user is active (and
            accepting terminal messages) on the host.  In any case the
            mail data is entered into the user's mailbox.  The mail
            transaction is successful if the message is delivered the
            mailbox.




 

                                                                        
August 1982                                                      RFC 821
Simple Mail Transfer Protocol                                           



      The same reply codes that are used for the MAIL commands are used
      for these commands.