Mail Server

1
Mail Server

• Fitri Setyorini

2
Content

• SMTP
• POP3
• How mail server works
• IMAP

3
Electronic Mail Overview

• Three major components
• user agents, mail servers, SMTP
• User Agent
• a.k.a. mail reader
• composing, editing, reading mail messages
• e.g., Eudora, Outlook, elm, Netscape Messenger
• Mail Servers
• mailbox contains incoming messages for user
• message queue of outgoing (to be sent) mail
  messages
• use SMTP protocol between mail servers to send
  email messages
• client sending mail server
• server receiving mail server gmail?

4
SMTP

• uses TCP to reliably transfer email message from
  client to server, port 25
• direct transfer sending server to receiving
  server
• three phases of transfer
• handshaking (greeting)?
• transfer of messages
• closure
• command/response interaction
• commands ASCII text
• response status code and phrase
• messages must be in 7-bit ASCII

5
(No Transcript)
6
(No Transcript)
7
Electronic Mail more on SMTP

• SMTP uses persistent connections
• SMTP requires message (header body) to be in
  7-bit ASCII
• SMTP server uses CRLF.CRLF to determine end of
  message

8
Electronic Mail message format

• SMTP protocol for exchanging email messages
• RFC 822 standard for text message format
• header lines, e.g.,
• To
• Date
• From
• Subject
• Message-ID
• different from SMTP commands!
• Read MAIL
• body
• the message, ASCII characters only

header
blank line
body
9
(No Transcript)
10
Electronic Mail MIME typesContent-Type
type/subtype parameters

• Text
• example subtypes plain, html
• Image
• example subtypes jpeg, gif
• Audio
• example 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

11
(No Transcript)
12
POP (Post Office Protocol)?

• POP is used to retrieve mail for a single user,
  typically the POP server has access from database
  email messages created by an SMTP server.
• POPv1 is launched on October 1984. It was
  published in RFC 918.
• POPv3 is the recently standard
• POP use port 110

13
(No Transcript)
14
How POP3 Works

• The server host starts the POP3 service by
  listening on TCP port 110.
• A client establishes a TCP connection with the
  server host.
• When the connection is established the server
  sends a greeting.
• The client and the server exchange commands and
  responses until the connection is closed or
  aborted.
• The server can respond with a positive status
  sending "OK" to the client or with a negative
  status sending "-ERR" to the client (both in
  uppercase).

15

• Authorization state
• In this state, the client sends identification
  to the server. This is implemented in two ways
  (More information on authentication is described
  in RFC 1734)
• - Using USER and PASS commands
• - Using APOP command
• Transaction state
• In this state, the client can issue commands for
  listing, retrieving, and deleting. Please note
  that the deleting action is not taken in this
  state. The client must send the QUIT command and
  then the server goes to the update state.
• Update state
• In this state, the server updates the mailbox
  according to the commands received from the
  client in the transaction state and the TCP
  connection ends. If the connection is broken for
  any reason before the quit command is received
  from the client, the server does not enter the
  update state.Thus, the server will not update
  anything.

16
Difference between POP3 and IMAP

• POP3 works by reviewing the inbox on the mail
  server, and downloading the new messages to your
  computer.  IMAP downloads the headers of the new
  messages on the server, then retrieves the
  message you want to read when you click on it. 
• When using POP3, your mail is stored on your PC.
  When using IMAP, the mail is stored on the mail
  server. Unless you copy a message to a "Local
  Folder" the messages are never copied to your PC.

17
Konfigurasi Postfix pada main.cf

• myhostname mail.jerapah.com
• mydomain jerapah.com
• myorigin myhostname
• inet_interfaces all