Web Server Administration : 1 Web Server Administration Chapter 8
Providing E-mail Services
Overview : 2 Overview Understand the e-mail environment
Understand e-mail protocols
Install and administer Microsoft Exchange 2000
Install and administer sendmail for Linux
Overview : 3 Overview Install and configure IMAP4 and POP3 servers for Linux
Configure e-mail clients
Understand Web-based e-mail clients
Understanding the E-mail Environment : 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
Exchange 2000 Goes Beyond E-mail Basics : 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
Role of DNS in E-mail Systems : 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.com.
The 10 refers to the priority of the e-mail server if there are multiple e-mail servers
E-mail System Terminology : 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
E-mail System Terminology : 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
E-mail Protocols : 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
Understanding SMTP : 10 Understanding SMTP The commands are processed by the SMTP server
Understanding SMTP : 11 Understanding SMTP The SMTP headers add descriptive information
Understanding SMTP : 12 Understanding SMTP Sample session
Commands and headers in bold
HELO WKS1
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 .
This is a simple message
.
QUIT
Understanding POP3 : 13 Understanding POP3 More simplistic than IMAP4
First step is to log on with user name and password
List, read, download, delete e-mail
Common POP3 commands : 14 Common POP3 commands
Sample POP3 Session-Major Components : 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@yahoo.com
Return-Path: xyz@yahoo.com
This is a sample message
.
DELE 1
+OK
QUIT
Understanding IMAP4 : 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
Common IMAP4 commands : 17 Common IMAP4 commands
Installing Microsoft Exchange 2000 : 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
Administering Exchange 2000 : 19 Administering Exchange 2000 Message Delivery Defaults
Administering Exchange Users : 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
Exchange 2000 Delivery Restrictions : 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
Installing and Configuring Sendmail for Linux : 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
Minimal sendmail.mc File : 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'
Installing and Configuring IMAP4 and POP3 for 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
Configuring E-mail Clients-Typical Information Required : 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
Web-based E-mail Clients : 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
Web-based E-mail Clients-Advantages : 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
Summary : 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