E-mail (SMTP, MIME)
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Message transfer protocol (SMTP) vs message format protocols (RFC
822, Multipurpose Internet Mail Extensions or MIME)
RFC 822: message consists of header and body
 Header fields: <type: value CRLF> (e.g., subject: hi!)
 Body: ASCII only
 Body separated by header with a blank line
 Content-type/length/encoding/description..
MIME extension (93 and 96): allows many different types of body types
(audio, images, Word documents, etc)
 MIME also defines multipart type, allowing multiple data types in
single message
Base64 encoding of 8-bit binary words in 6-bit printable ASCII
characters
 Maps every 3-byte group of binary message to 4 6-bit characters
 MIME also supports 7-bit ASCII encoding of text-only messages
Default SMTP server listening port : 25
From mike@cc.gatech.edu Fri Oct 25 15:39:08 2002
Received: from sark.cc.gatech.edu (sark.cc.gatech.edu [130.207.7.23])
by tokyo.cc.gatech.edu (8.11.6/8.11.6) with ESMTP id g9PJd7K29064
for <dovrolis@tokyo.cc.gatech.edu>; Fri, 25 Oct 2002 15:39:07 -0400 (EDT)
Received: from boris.cc.gatech.edu (boris.cc.gatech.edu [130.207.6.141])
by sark.cc.gatech.edu (8.11.6/8.11.6) with ESMTP id g9PJd5a08589
for <dovrolis@cc.gatech.edu>; Fri, 25 Oct 2002 15:39:05 -0400 (EDT)
Received: from [130.207.6.84] (mccracken.cc.gatech.edu [130.207.6.84])
by boris.cc.gatech.edu (8.11.6/8.11.6) with ESMTP id g9PJd5709928
for <dovrolis@cc.gatech.edu>; Fri, 25 Oct 2002 15:39:05 -0400 (EDT)
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Message-Id: <v04020a23b9df4dcf85b5@[130.207.6.84]>
In-Reply-To: <Pine.GSO.4.44.0210230920560.1561-100000@tokyo.cc.gatech.edu>
Date: Fri, 25 Oct 2002 15:40:17 -0400
To: Constantine <dovrolis@cc.gatech.edu>
From: Mike McCracken <mike@cc.gatech.edu>
Subject: Re: MS thesis/project
Content-Length: 1011
Status: RO
X-Status: A
X-Keywords:
X-UID: 6561
(email body omitted..)
Mike
SMTP: email message transfer
Mail
reader
Mail gateway
Mail
daemon
Mail
daemon
SMTP/TCP
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Mail
reader
Mail
daemon
SMTP/TCP
Mail readers, daemons, and gateways
Network transfer takes place over TCP
Mail gateways can buffer pending messages for days, are always
up, and they can also be used for email preprocessing (e.g.,
spam detection)
Each SMTP session is a sequence of text-based
commands/responses between two sendmail daemons
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As generated by rth's mailer and handed off to mail.bieberdorf.edu:
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From: rth@bieberdorf.edu (R.T. Hood)
To: tmh@immense-isp.com
Date: Tue, Mar 18 1997 14:36:14 PST
X-Mailer: Loris v2.32
Subject: Lunch today?
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As they are when mail.bieberdorf.edu transmits the message to mailhost.immense-isp.com:
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Received: from alpha.bieberdorf.edu (alpha.bieberdorf.edu [124.211.3.11]) by
mail.bieberdorf.edu (8.8.5) id 004A21; Tue, Mar 18 1997 14:36:17 -0800 (PST)
From: rth@bieberdorf.edu (R.T. Hood)
To: tmh@immense-isp.com
Date: Tue, Mar 18 1997 14:36:14 PST
Message-Id: <rth031897143614-00000298@mail.bieberdorf.edu>
X-Mailer: Loris v2.32
Subject: Lunch today?
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As they are when mailhost.immense-isp.com finishes processing the message and stores it for tmh
to retrieve:
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Received: from mail.bieberdorf.edu (mail.bieberdorf.edu [124.211.3.78]) by
mailhost.immense-isp.com (8.8.5/8.7.2) with ESMTP id LAA20869 for <tmh@immenseisp.com>; Tue, 18 Mar 1997 14:39:24 -0800 (PST)
Received: from alpha.bieberdorf.edu (alpha.bieberdorf.edu [124.211.3.11]) by
mail.bieberdorf.edu (8.8.5) id 004A21; Tue, Mar 18 1997 14:36:17 -0800 (PST)
From: rth@bieberdorf.edu (R.T. Hood)
To: tmh@immense-isp.com
Date: Tue, Mar 18 1997 14:36:14 PST
Message-Id: <rth031897143614-00000298@mail.bieberdorf.edu>
X-Mailer: Loris v2.32
Command Description
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DATA Begins message composition.
EXPN <string> Returns names on the specified mail list.
HELO <domain> Returns identity of mail server.
HELP <command> Returns information on the specified command.
MAIL FROM <host> Initiates a mail session from host.
NOOP Causes no action, except acknowledgement from server.
QUIT Terminates the mail session.
RCPT TO <user> Designates who receives mail.
RSET Resets mail connection.
SAML FROM <host> Sends mail to user terminal and mailbox.
SEND FROM <host> Sends mail to user terminal.
SOML FROM <host> Sends mail to user terminal or mailbox.
TURN Switches role of receiver and sender.
VRFY <user> Verifies the identity of a user.
Response Codes
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Server returns response codes to client:
2xx everything is fine, go on
 4xx temporary problem, try again later
 5 xx permanent error, give up
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Mail session