The first version of the SMTP protocol was defined in RFC 821. The current standard for SMTP is defined in RFC 5321 considering only RFC 821 what are the main commands of the SMTP protocol?

The following are the explanation for each command, with the SMTP protocol considering only RFC 821.

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.