Chapter 8
Providing E-mail Services
Overview
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Understand the e-mail environment
Understand e-mail protocols
Administering the Microsoft Exchange 2000
Installation and administering sendmail for
Linux
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Install and configure IMAP4 and POP3 servers
for Linux
Understanding the E-mail Environment
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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
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Sendmail (Linux)
Exchange (Windows)
Exchange 2000
Goes Beyond E-mail Basics
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Instant messaging
Unified messaging platform
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Chat service
URL addressing
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Single inbox for e-mail, voicemail, fax
Use a single URL to access stored data
Audio and video conferencing
What about the goofy cartoons (emotions) you can
include in your email?
Role of DNS in E-mail Systems
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Sending email messages requires configuring DNS
A domain name, such as technowidgets.com, needs to be associated with
two IP addresses
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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
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MX 10 mail.technowidgets.com.
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
E-mail System Terminology
MTA (Mail Transfer Agent)
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MUA (Mail User Agent)
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Accepts e-mail from clients and
sends e-mail to another MTA
for storage
Exchange 2000, sendmail
E-mail client software
Formats the message and
prepares it for sending to MTA
Outlook, KMail
MDA (Mail Delivery Agent)
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Part of the email server
Delivers e-mail from server to
MUA
Exchange 2000, imap-2001
M Em
es a
sa i l
ge
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`
email Client
Sender
(MUA)
Email Server
(MTA)
Email Server
(MTA)
`
email Client
Receiver
(MUA)
E-mail System Terminology
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Masquerading
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Replace actual host name with domain name
Actual host name is replaced
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mail2.technowidgets.com  ffarid@ mail2.technowidgets.com
becomes ffarid@ technowidgets.com (masking the full host
name)
Relaying
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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
E-mail Protocols
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SMTP (Simple Mail Transfer Protocol)
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POP3 (Post Office Protocol)
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Text-based protocol used to send e-mail messages
Does not concern any concerns about security
Both client and server use it
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)
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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
Understanding SMTP
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The commands are processed by the
SMTP server
Command
Purpose
HELO
Identifies the domain sending the message
DATA
Indicates the body of the message
VRFY
Verifies the e-mail user
QUIT
Ends the SMTP session
Understanding SMTP
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The SMTP headers add descriptive information
Header
Description
MAIL FROM:
Identifies who is sending the message (required)
RCPT TO:
Identifies the recipient of the message (required)
RECEIVED:
Identifies the e-mail server that processed the message
DATE:
Indicates the date of the e-mail
FROM:
Shows the e-mail address as it is typically displayed in an e-mail client
SUBJECT:
Shows the subject of the e-mail message
TO:
Shows the recipient as it is typically displayed in an e-mail client
CC:
Sends copies of the message to a list of e-mail addresses
BCC:
Sends copies of the message to a list of e-mail addresses but does not
display the e-mail addresses
Understanding SMTP
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Response Code
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@yahoo.com
250 2.1.0 xyz@yahoo.com....Sender OK
RCPT TO: cbranco@technowidgets.com
250 2.1.5 cbranco@technowidgets.com
DATA
354 Start mail input; end with <CRLF>.<CRLF>
This is a simple message
.
Carriage Return
QUIT
Line feed
Understanding POP3
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Less complex than IMAP4
First step is to logon with user name and
password
List, read, download, delete e-mail
Common POP3 commands
Command
Description
USER username Connects to POP3 server based on user name
PASS password Enters the password for the user, as in PASS: Ax6yy
LIST
Displays the message number followed by the number of
characters in the message
UIDL
Displays the unique ID for each message
RETR n
Replaces the n with a message number to retrieve that message
TOP n lines
Instead of retrieving the whole message, retrieves the number of
lines designated by the lines parameter for message number n
DELE n
Deletes message number n from the server
QUIT
Ends the session
Understanding IMAP4
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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)
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\Recent
\Seen
\Answered
\Flagged
\Deleted
\Draft
Common IMAP4 commands
Command
Description
LOGIN username
password
Log on to the server with your user name and password,
which are unencrypted.
SELECT mailbox
Select a mailbox before you perform mail tasks. The
default mailbox is called inbox. The response gives a
summary of mailbox information.
FETCH message(s)
item(s)
Retrieve messages. The message(s) parameter gives the
message number. The item(s) parameter determines
what part of the message is fetched—that is, individual
header items or the body of the text.
STORE message(s)
flags
Change the flags associated with a message. Typically,
this command is used to mark messages to be deleted,
undeleted, or identified as unread.
LOGOUT
End the IMAP4 session.
Installing Microsoft Exchange 2000
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Install SMTP is part of IIS Web Server
Install NNTP (Network News Transport
Protocol), also a part of IIS
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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
Installing and Configuring Sendmail for Linux
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Installed sendmail
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includes SMTP only
Configure sendmail through a macro called m4
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m4 /etc/mail/sendmail.mc >/etc/mail/sendmail.cf
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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
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'
Configuring E-mail ClientsTypical Information Required
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SMTP server IP address
Your e-mail address
Your e-mail password
POP3 or IMAP4 server IP address
Summary
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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
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SMTP, POP3, and IMAP4
Projects and Labs
Linux Projects
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Project 8-1
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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
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telnet localhost 25  send a message to zzz@yyy.com
Do cat /var/spool/mail/ zzz@yyy.com  you should see the message
Project 8-2
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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
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
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Configure Kmail in Linux – create two users and send emails to each other
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Project 8-7
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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!
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Windows Lab
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Do project 8-9 page 437
Send email from a Linux server to a Windows
machine.
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If you Install Exchange 2000, and do you
will receive Extra credit!
Page 389- Installation steps!
Page 392-Adminstering
Project 8-3 page 429
Homework (April. 5rd) submit through WebCT
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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? )
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What is qmail in Linux? Can we use it instead of sendmail? What is it used for?
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Extra Credit - Write a step-by-step procedure to install a software product in Linux that allows webmail.
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 – Don’t 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
Errors in the book
Linux Email Server Labs
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Install sendmail (page 400 step 1-9)
Configure the sendmail as sendmail.mc and store it
in >/etc/mail/
Install and configure IMP4 and POP3 (page 404)
Configure email client in Linux: Kmail  installed
automatically – create an account
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If you have problem with Kmail you may need to reinstall
Kmail