SMTP has a few more commands:
SEND command SOML command SAML command
 

Exchange of email using TCP/IP - page 1
 Basically, email consist of:
(1) The envelope  (2) Headers   (3) Message body - page 2
 

(1) Envelope
rfc 821 specifies the contents and interpretation of the envelope--used by the MTA's for delivery specified by these two SMTP commands (MAIL From: and RCPT To:)
MAIL From:<mable@sun.tuc.test.org>
RCPT To:<mable@test.org>

 

(2) Headers are used by the user agent and each header field contains a name, followed by a colon, followed by the field value.
Received: by sun.tuc.test.org. (4.1/SMI-4.1)
id AA01301; Tue, 21 May 98 11:37:22 MST
 Message-Id: <6210181836.AA00502@sun.tuc.test.org.>
From: mable@sun.tuc.test.org (Mable Merliney)
Reply-To: mable@test.org
X-Phone: +0 202 671 2761
X-Mailer: Mail User’s Shell (9.1.0 12/02/98)
To: mable@test.org
Subject: testing

Headers beginning with an X- are user-defined fields. RFC 822 specifies the format and interpretation of the header fields.

(3) Message body is the content of the message from the sender to the recipient and transferred using the DATA command--the headers are sent first, followed by a blank line, followed by the body. Each line transferred using the DATA command must be less than 1000 bytes.

The user agent takes what the sender specify as a body, adds some headers and passes the result to the MTA

The MTA adds a few headers, adds the envelope and sends the result to another MTA.

Notes: The term "content" used, normally means the combination of headers and the body--which is sent by the client with the DATA command.

  
 
 


SMTP has a few more commands:

SEND command SOML command SAML command
 begin a mail transaction, once started a mail transaction consists of HELO, MAIL FROM and one or more RCPT commands, follows by DATA command. SEND SOML SAML replaces the MAIL command and allow mails to be delivered directly to the recipient mailbox or user terminal.

Help command ask the receiver machine to send help information to the sender HELP request command.

RSET command that aborts current mail transaction and causes both ends to reset and any stored information about sender, recipients or mail data is discarded.

VRFY command lets the client ask the sender to verify a recipient address, identifies a user, name, specified mailbox and returned a reply, without sending mail to the recipient.

NOOP command force the server to respond with an OK reply code 200 - NOOP command does nothing else.

EXPN expands a mailing list, asks the receiver to confirm that the argument identifies a mailing list, and if yes, return the membership of that list with full name of the users and specified mailboxes.

TURN command lets the client and server switch roles,
to send mail in the reverse direction without having to create a new one TCP connection. The receiver must send an OK reply and then take on the role of the sender-SMTP or send a refusal 502 reply and retain the role of the receiver-SMTP.

HELP  NOOP   EXPN  and VRFY commands
can be used at any time during a session between SMTP mail machine. See Basic email delivery or How Email Works?

  


100% effective.
I recommend it.

   The easies way to stop email spam, virus getting
into your PC
 Free
2-Try
 
  Free eBook Sun Tzu
 Art of War - "Leaders who takes on the role of the commander, without understanding the strategy of warfare, invite defeat."
 

 
 

Can't find what you need?
 Try Google....

Google
  .
©Copyright June 2002  Permission to re-print,
please click here


Any feed-back
or suggestions?
Please drop us a note :o)