Providing E-mail Services

1
Chapter 8

• Providing E-mail Services

2
Overview

• Understand the e-mail environment
• Understand e-mail protocols
• Administering the Microsoft Exchange 2000
• Installation and administering sendmail for Linux
  
• Install and configure IMAP4 and POP3 servers for
  Linux

3
Understanding the E-mail Environment

• E-mail evolved from a variety of proprietary
  systems
• In the 1980s and 1990s, people often had e-mail
  addresses on a number of systems
• Even as late as 1997, many email servers were not
  able to take advantage of Internet e-mail
• Most common email server products
• Sendmail (Linux)
• Exchange (Windows)

4
Exchange 2000 Goes Beyond E-mail Basics

• Instant messaging
• Unified messaging platform
• Single inbox for e-mail, voicemail, fax
• Chat service
• URL addressing
• Use a single URL to access stored data
• Audio and video conferencing
• What about the goofy cartoons (emotions) you can
  include in your email?

5
Role of DNS in E-mail Systems

• Sending email messages requires configuring DNS
• A domain name, such as technowidgets.com, needs
  to be associated with two IP addresses
• One IP address can be for a Web site
• Another IP address is for e-mail
• To associate a domain name, or any other host
  name, with the IP address of an e-mail server,
  you need a mail exchange (MX) record
• technowidgets.com. IN MX 10 mail.technowidgets.co
  m.
• The 10 refers to the priority of the e-mail
  server if there are multiple e-mail servers
• IN indicating the domain name
• MX representing a Mail Exchange (MX) record
  other options could be A or NS

6
E-mail System Terminology

• MTA (Mail Transfer Agent)
• Accepts e-mail from clients and sends e-mail to
  another MTA for storage
• Exchange 2000, sendmail
• MUA (Mail User Agent)
• E-mail client software
• Formats the message and prepares it for sending
  to MTA
• Outlook, KMail
• MDA (Mail Delivery Agent)
• Part of the email server
• Delivers e-mail from server to MUA
• Exchange 2000, imap-2001

7
E-mail System Terminology

• Masquerading
• Replace actual host name with domain name
• Actual host name is replaced
• mail2.technowidgets.com ? ffarid_at_
  mail2.technowidgets.com becomes ffarid_at_
  technowidgets.com (masking the full host name)
• Relaying
• The process of sending e-mail to an intermediate
  e-mail server (MTA) before the message is
  transmitted to its final destination
• When single MTA is available, relaying should not
  be allowed from the Internet because spammers
  could use it to send e-mail

8
E-mail Protocols

• SMTP (Simple Mail Transfer Protocol)
• Text-based protocol used to send e-mail messages
• Does not concern any concerns about security
• Both client and server use it
• POP3 (Post Office Protocol)
• To retrieve e-mail
• Email client uses it to read, list, and delete
  email messages
• Typically, all messages are downloaded to a
  client
• IMAP4 (Internet Mail Access Protocol)
• More complex than POP3
• To retrieve e-mail
• E-mail stays on the server and can be retrieved
  from any computer that has an email client and
  supports the protocol
• You can create folders on server to store e-mail

9
Understanding SMTP

• The commands are processed by the SMTP server

10
Understanding SMTP

• The SMTP headers add descriptive information

11
Understanding SMTP

• Sample session (commands and headers)
• HELO WKS1 ? Sending the name of the host
• 250 web1.technowidgets.com Hello 127.0.0.1
• MAIL FROM XYZ_at_yahoo.com
• 250 2.1.0 xyz_at_yahoo.com....Sender OK
• RCPT TO cbranco_at_technowidgets.com
• 250 2.1.5 cbranco_at_technowidgets.com
• DATA
• 354 Start mail input end with ltCRLFgt.ltCRLFgt
• This is a simple message
• .
• QUIT

Response Code
Carriage Return Line feed
12
Understanding POP3

• Less complex than IMAP4
• First step is to logon with user name and
  password
• List, read, download, delete e-mail

13
Common POP3 commands
14
Understanding IMAP4

• Messages remain on server
• Requires much more space on server
• To keep track of the status of messages, flags
  are used (For example your free yahoo account)
• \Recent
• \Seen
• \Answered
• \Flagged
• \Deleted
• \Draft

15
Common IMAP4 commands
16
Installing Microsoft Exchange 2000

• Install SMTP is part of IIS Web Server
• Install NNTP (Network News Transport Protocol),
  also a part of IIS
• Used for newsgroup
• Active Directory is required for Exchange
• Once the above are installed, the Exchange wizard
  guides you through a simple installation
• Then, to use Exchange 2000 on Windows Server
  2003, install Exchange 2000 Service Pack 3 is
  required

17
Installing and Configuring Sendmail for Linux

• Installed sendmail
• includes SMTP only
• Configure sendmail through a macro called m4
• m4 /etc/mail/sendmail.mc gt/etc/mail/sendmail.cf
• The macro is processed and sendmail.cf is created
• There are many advanced features of sendmail that
  make configuring it substantially difficult
• There are other e-mail servers, such as qmail,
  that are easier

18
Minimal sendmail.mc File

• divert(-1)
• include(/usr/share/sendmail-cf/m4/cf.m4')
• OSTYPE(linux')
• define(PROCMAIL_MAILER_PATH',/usr/bin/procmail')
  dnl
• FEATURE(local_procmail,',procmail -t -Y -a h
  -d u')dnl
• MAILER(smtp)dnl
• MAILER(procmail)dnl
• Cwtechnowidgets.com

Notice that the strings are enclosed with a
backtick and an apostrophe as in linux'
19
Configuring E-mail Clients-Typical Information
Required

• SMTP server IP address
• Your e-mail address
• Your e-mail password
• POP3 or IMAP4 server IP address

20
Summary

• E-mail has evolved over the years
• Microsoft Exchange 2000 and sendmail are the two
  of the most popular e-mail server products
• DNS plays a central role in messaging
• Three major protocols are involved in e-mail
• SMTP, POP3, and IMAP4

21
Projects and Labs
22
Linux Projects

• Project 8-1
• Make sure your DNS works
• Go to page 374-375 and make sure you have added
  the two email entries in your reverse lookup
  table
• Make sure sendmail is installed You should have
  checked the mail server box
• If you have to install it, there is no need to
  Start the program
• You should have a /etc/mail/sendmail.mc file.
  Make a back up of this file and modify it
  according to the text page 424
• Using m4 utility create sendmail.cf page 424 step
  5
• Create a telnet session to send email
• telnet localhost 25 ? send a message to
  zzz_at_yyy.com
• Do cat /var/spool/mail/ zzz_at_yyy.com ? you should
  see the message
• Project 8-2
• Test IMAP4/POP3
• telnet localhost 143 ? Results must be similar to
  Page 428
• telnet localhost 110 ? Results must be similar to
  Page 429
• Project 8-5
• Configure Kmail in Linux create two users and
  send emails to each other
• Project 8-7
• Do cat /var/spool/mail ? display all the messages
  (header and contents) the user has received
• Two servers should be able to send email messages
  to each other!

23
Windows Lab

• Do project 8-9 page 437
• Send email from a Linux server to a Windows
  machine.

• If you Install Exchange 2000, and do you will
  receive Extra credit!
• Page 389- Installation steps!
• Page 392-Adminstering
• Project 8-3 page 429

24
Homework (April. 5rd) - submit through WebCT

• How can you access your email by using a browser
  in Linux? (Read chapter 8 pages 417-419 in
  Windows Web-based email product is OWA (Outlook
  Web Access). OWA uses XML or Dynamic HTML to
  transfer format processing from the server to the
  browser). Is there a similar capability in
  Linux? Is there a software to support Webmail for
  Linux? Are there software products that allow
  transferring format processing from the server to
  the browser? )
• Extra Credit - Write a step-by-step procedure to
  install a software product in Linux that allows
  webmail.
• What is qmail in Linux? Can we use it instead of
  sendmail? What is it used for?
• Extra Credit Implement qmail on a server in the
  lab or write a step-by-step procedure. (Do not
  copy the procedure from the Web I have already
  read that! To get extra credit, you should write
  your own SHORT version)
• Find a Linux-based package that can be configured
  to allow instant messaging, (or audio and video
  conferencing). What is the difference between
  Gaim and Kopete?
• What is multicasting? What is source tree
  multicasting? Does email server utilizes
  multicasting? How?
• One way spammers send unsolicited email is by
  masquerading their message such that they appear
  to have come from your organization or some safe
  source. Elaborate on such spamming techniques.
  What do they do so that you cannot detect them?
  (Read about spamming technique. There are lots of
  ways to send spam and not get detected There
  are many interesting articles about this in
  PCWORLD.com Dont just copy and paste I have
  read them! Just write a brief summary)
• Let me know if you find errors in the book!

Maximum Extra Credit will be 20 points
25
Errors in the book
26
Linux Email Server Labs

• Install sendmail (page 400 step 1-9)
• Configure the sendmail as sendmail.mc and store
  it in gt/etc/mail/
• Install and configure IMP4 and POP3 (page 404)
• Configure email client in Linux Kmail ?
  installed automatically create an account
• If you have problem with Kmail you may need to
  reinstall Kmail