Web Server Administration

1
Web Server Administration

• Chapter 8
• Providing E-mail Services

2
Overview

• Understand the e-mail environment
• Understand e-mail protocols
• Install and administer Microsoft Exchange 2000
• Install and administer sendmail for Linux

3
Overview

• Install and configure IMAP4 and POP3 servers for
  Linux
• Configure e-mail clients
• Understand Web-based e-mail clients

4
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, Exchange 5.5 was not
  designed to take advantage of Internet e-mail
• An add-on gave Exchange the ability to send and
  receive e-mail over the Internet

5
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

6
Role of DNS in E-mail Systems

• 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 an 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

7
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
• Outlook, KMail
• MDA (Mail Delivery Agent)
• Delivers e-mail from server to MUA
• Exchange 2000, imap-2001

8
E-mail System Terminology

• Masquerading
• Replace actual host name with domain name
• Relaying
• The process of sending e-mail to an intermediate
  e-mail server before the message is transmitted
  to its final destination
• This should not be allowed from the Internet
  because spammers could use it to send e-mail
• Spammer
• Someone who sends unsolicited e-mail, typically
  to try to sell something

9
E-mail Protocols

• SMTP (Simple Mail Transfer Protocol)
• To send e-mail messages
• POP3 (Post Office Protocol)
• To retrieve e-mail
• Typically, all messages are downloaded to a
  client
• IMAP4 (Internet Mail Access Protocol)
• To retrieve e-mail
• E-mail stays on the server
• You can create folders on server to store e-mail

10
Understanding SMTP

• The commands are processed by the SMTP server

11
Understanding SMTP

• The SMTP headers add descriptive information

12
Understanding SMTP

• Sample session
• Commands and headers in bold
• HELO WKS1
• 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 .
• This is a simple message
• .
• QUIT

13
Understanding POP3

• More simplistic than IMAP4
• First step is to log on with user name and
  password
• List, read, download, delete e-mail

14
Common POP3 commands
15
Sample POP3 Session-Major Components

• USER cbranco
• OK
• PASS pass
• OK User successfully logged on.
• LIST
• OK 1 404
• 1 404
• .
• RETR 1
• OK
• Received from WKS1 (127.0.0.1) by
  web1.technowidgets.com
• From xyz_at_yahoo.com
• Return-Path xyz_at_yahoo.com
• This is a sample message
• .
• DELE 1
• OK
• QUIT

16
Understanding IMAP4

• Messages remain on server
• Requires much more space on server
• To keep track of the status of messages, flags
  are used
• \Recent
• \Seen
• \Answered
• \Flagged
• \Deleted
• \Draft

17
Common IMAP4 commands
18
Installing Microsoft Exchange 2000

• SMTP is part of IIS, not Exchange, and needs to
  be installed
• NNTP (Network News Transport Protocol) needs to
  be installed before Exchange and is also part of
  IIS
• Active Directory is required for Exchange
• Once the above are installed, the Exchange wizard
  guides you through a simple installation
• To use Exchange 2000 on Windows Server 2003,
  Exchange 2000 Service Pack 3 is required

19
Administering Exchange 2000

• Message Delivery Defaults

20
Administering Exchange Users

• When you add a user, you have the option to
  create a mailbox
• By default, the e-mail name is the same as the
  user name but you can change it

21
Exchange 2000 Delivery Restrictions

• You can restrict the size of messages being sent
  and received
• The e-mail names of senders can be restricted too

22
Installing and Configuring Sendmail for Linux

• Installed from an rpm file
• Configure sendmail through a macro processor
  called m4
• m4 /etc/mail/sendmail.mc /etc/mail/sendmail.cf
• 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

23
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'
24
Installing and Configuring IMAP4 and POP3 for
Linux

• Both IMAP4 and POP3 are included in the imap-2001
  package
• Once installed, you have to enable the daemons by
  either editing their configuration files such as
  /etc/xinetd.d/imap or using chkconfig
• chkconfig imap on
• Then you restart xinetd to recognize the changes
• service xinetd restart

25
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

26
Web-based E-mail Clients

• Web-based e-mail clients allow you to use your
  browser
• Exchange 2000 can be configured for Web-based
  e-mail using Outlook Web Access
• Public sites, such as Microsoft's Hotmail and
  Yahoo! Mail, have been very popular

27
Web-based E-mail Clients-Advantages

• Because a browser is used, no client
  configuration is needed
• The lack of configuration can significantly
  reduce support costs
• No specialized client software is needed
• Users are not required to retrieve e-mail from
  specific computers that have been configured for
  them
• POP3 or IMAP4 protocols are not required, which
  reduces server-side support
• Because Web-based e-mail is not constrained by
  POP3 or IMAP4 protocols, a richer environment can
  be developed that extends beyond basic e-mail

28
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