Answer:
The following are the explanation for each command, with the SMTP protocol considering only RFC 821.
Step-by-step explanation:
The key commands of the SMTP protocols which take the RFC 821 into account are as follows:
HELLO -
A client receives that order to describe himself
HELP-
It asks by the receivers to submit the command information as argument
QUIT -
It is used to terminate the message.
-FROM MAIL
The clients use it to acknowledge the message's sender.
NOOP -
The client does not use any procedure to verify the receiver status as required by the receiver's reply form.
RCPT-
The user needs it to determine the intended beneficiary.
SAML-
It sends or ends the specific mail which is sent to the mailbox or the SAML
RESET-
The existing email transaction is aborted.
SEND- The mail to be sent by the recipient's terminal, not its mailbox, is specified.
TURN-
It allows the sender to change position and recipients.
VRFY-
Verification checks the recipient's address.