1. Sending and Receiving Mails

2. SMTP (Simple Mail Transfer Protocol)
POP3 (Post Office Protocol version 3)
IMAP4 (Internet Message Access Protocol version 4)
MIME (Multipurpose Internet Mail Extension)

3. SMTP RFCs RFC 821: Simple Mail Transfer Protocol Related RFCs
RFC 822 (Standard for the format of ARPA Internet text messages)
RFC 1521 (MIME)
RFC (POP3)
RFC (IMAP4)
Well known port : 25 (TCP)

4. ESMTP Extended Simple Mail Transfer Protocol
RFC 1869: SMTP Service Extensions
RFC 1870: SMTP Service Extension for Message Size Declaration
RFC 1891: SMTP Service Extension for Delivery Status Notifications
RFC 2554: SMTP Service Extension for Authentication
Two major differences from SMTP:
Support 8-bit MIME encoding
Support SMTP authorization

5. SMTP: Simple Mail Transfer Protocol
Three Components:
user agents: “mail readers”
mail servers: “mailbox; mail queue”
smtp: simple mail transfer protocol
protocol between mail servers
protocol between mail the server and the client

6. SMTP: agents/servers user agents: “mail readers” mail servers:
composing, editing, reading mail messages
e.g., Outlook, Eudora, pine, elm, Netscape Messenger
send and receive outgoing and incoming messages to mail server
mail servers:
mailbox: contains incoming messages (yet to be read) for user
message queue: contains outgoing (to be sent) mail messages

7. SMTP Process Contact server on well known port (25)
ASCII oriented command/response
methodology
contact server
wait for greeting
send HELO
wait for response
send command
repeat last two

8. SMTP Commands HELP MAIL RCPT DATA
identifies the client to the server, fully qualified domain name, only sent once per session
MAIL
initiate a message transfer, fully qualified domain of originator
RCPT
follows MAIL, identifies an addressee, typically the fully qualified name of the addressee
for multiple addressees use one RCPT for each addressee
DATA
send data line by line
<cr>.<cr> tells server data transfer is over

9. SMTP Commands RSET SEND , SOML , SAML VRFY EXPN
tells server to abort current message and clear all of it buffers
same state as after HELO
SEND , SOML , SAML
like MAIL, outdated not used any more
VRFY
ask server to verify a user name
server replies positively of it knows user, negatively if not
EXPN
ask server to confirm mailing list alias
server reply is multi-line, one per user

10. SMTP Commands HELP NOOP QUIT TURN ask server for help
by itself get a list of server supported commands
<string> get help for that command
NOOP
ask server to respond with a positive reply
QUIT
tell server that client is ending session
server replies positively and closes connection
TURN
reverse roles of client and server
outdated, rarely used on modern internet

11. Reply codes 211 - System status or help ready 214 - Help message
220 - <domain> Service ready
221 - <domain> Service closing transmission channel
250 - Requested mail action OK, ready
251 - User not local, will forward to <forward path>
354 - Start mail input; end with <crlf>.<crlf>
421 - <domain> Service not avail, closing transmission channel
450 - Requested mail action not taken, mailbox not available
451 - Requested action aborted, local error
452 - Requested action not taken, insufficient storage
500 - Syntax error, command unrecognized
501 - Syntax error in parameters
502 - Command not implemented
503 - Bad sequence of commands
504 - Command Parameter not implemented

12. Reply codes (more)
550 - Requested action not taken, mailbox unavailable
551 - User not local, please try <forward path>
552 - Requested mail action not taken; exceeded storage allocation
553 - Requested action not taken, mailbox name not allowed
554 - Transaction failed

13. Reply Code (more) 353 Indicates success, failure, or incomplete
The category of error message
The specific message for that category
첫번째
1-3 Success
4. Temp negative
5 failure
두번째
0 syntax
2 connection
5 mail
Expn 모두 보여줌.. (그룹 지정시) 일반적으로 모두 disable 됨(보안적 문제)

14. SMTP: Example mail from:javamail@csie.ncu.edu.tw
telnet smtp.csie.ncu.edu.tw 25
220 relay2.csie.ncu.edu.tw ESMTP Sendmail / ; Thu, 11 Mar :54: (CST)220 mailServer.iitb.edu
helo smtp.csie.ncu.edu.tw
250 relay2.csie.ncu.edu.tw Hello adsl HCON.sparqnet.net [ ], pleased to meet you
mail
Sender ok
rcpt
Relaying denied. Proper authentication required.
rcpt
Recipient ok

15. SMTP: Example (more) data
354 Please start mail input.
date: subject: This is a test. from: to: reply-to: Hi, JR This is a test. .
250 Mail queued for delivery.
quit
221 Closing connection. Good bye.

16. ESMTP: Example telnet smtp.csie.ncu.edu.tw 25
220 relay2.csie.ncu.edu.tw ESMTP Sendmail / ; Thu, 11 Mar :54: (CST)220 mailServer.iitb.edu
ehlo smtp.csie.ncu.edu.tw
250-relay2.csie.ncu.edu.tw Hello adsl HCON.sparqnet.net [ ], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH LOGIN PLAIN
250-STARTTLS
250-DELIVERBY
250 HELP

17. ESMTP: Example help 214-2.0.0 This is sendmail version 8.12.11
Topics:
HELO EHLO MAIL RCPT DATA
RSET NOOP QUIT HELP VRFY
EXPN VERB ETRN DSN AUTH
STARTTLS
For more info use "HELP <topic>".
To report bugs in the implementation send to
For local information send to Postmaster at your site.
End of HELP info

18. Mail message format header lines:
RFC 822: Standard for the format of ARPA Internet text messages
header lines:
Date:
From:
To:
Reply-to:
Subject:
etc...

19. Multimedia extensions
additional lines in message header declare MIME content type
MIME version
From:
To:
Subject: Picture.
MIME-Version: 1.0
Content-Transfer-Encoding: base64
Content-Type: image/jpeg
base64 encoded data .....
......base64 encoded data .
method used
to encode data
multimedia datatype,
parameter declaration
encoded data

20. MIME [RFC 2045, 2056] MIME: Multimedia Extension Types:
Text: subtypes: plain, html
Image: subtypes: jpeg, gif
Audio: subtypes: basic (8-bit mu-law encoded), 32kadpcm (32 kbps coding)
Video: example subtypes: mpeg, quicktime
Application: other data that must be processed by reader before “viewable”; example subtypes: msword, octet-stream

21. POP3 POP3(Post Office Protocol 3) defined RFC1939 Used TCP port 110
No state information between client and the mail server
Client side mail management
No security
POP3 progresses through three phases
Authorization – user / pass
Transaction – list / retr / dele / stat
Update – quit
Two Operation modes
Download-and-delete mode
Download-and-keep keep

22. POP3 Commands USER name valid in the AUTHORIZATION state PASS string
QUIT
STAT valid in the TRANSACTION state
LIST [msg]
RETR msg
DELE msg
NOOP
RSET
QUIT valid in the UPDATE state

23. POP3 Replies
+OK
-ERR

24. POP3 Hamburger</home/staff/hkkim>9% telnet rtlab.skku.ac.kr 110
Trying
Connected to rtlab.skku.ac.kr.
Escape character is '^]'.
+OK Qpopper (version 4.0.3) at imtl.skku.ac.kr starting.
user hkkim
+OK Password required for hkkim.
pass tlftlrks
+OK hkkim has 3 visible messages (0 hidden) in 3043 octets.
list
+OK 3 visible messages (3043 octets)
1 1483
2 780
3 780 .
retr 1
+OK 1483 octets
Received: from brunhild ([ ………
dele 1
+OK Message 1 has been delted.
quit
+OK Pop server at imtl.skku.ac.kr signing off.
Connection closed by foreign host.
Download-and-delete
Authorization
Transaction
Update

25. Term project problems
Design a sending mail program supporting ESMTP AUTH
Design a receiving mail program supporting MIME