chapter 8 providing e-mail services. overview understand the e-mail environment understand e-mail...
TRANSCRIPT
Chapter 8Providing E-mail Services
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
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)
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?
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.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)
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
` `
Email Server(MTA)
Email Server(MTA)
email ClientSender (MUA)
email Client Receiver(MUA)
Mes
sage
E-mail System Terminology Masquerading
Replace actual host name with domain name Actual host name is replaced
mail2.technowidgets.com ffarid@ mail2.technowidgets.com becomes ffarid@ 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
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
Understanding SMTP 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 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 Sample session (commands and headers)HELO WKS1 Sending the name of the host250 web1.technowidgets.com Hello [127.0.0.1]MAIL FROM: [email protected] 250 2.1.0 [email protected] OKRCPT TO: [email protected] 2.1.5 [email protected] Start mail input; end with <CRLF>.<CRLF>This is a simple message.QUIT
Response Code
Carriage ReturnLine feed
Understanding POP3 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 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
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 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
Installing and Configuring Sendmail for Linux
Installed sendmail includes SMTP only
Configure sendmail through a macro called m4 m4 /etc/mail/sendmail.mc >/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
Minimal sendmail.mc Filedivert(-1)include(`/usr/share/sendmail-cf/m4/cf.m4')OSTYPE(`linux')define(`PROCMAIL_MAILER_PATH',`/usr/bin/procmail')dnlFEATURE(local_procmail,`',`procmail -t -Y -a $h -d $u')dnlMAILER(smtp)dnlMAILER(procmail)dnlCwtechnowidgets.com
Notice that the strings are enclosed with a backtick and an apostrophe as in `linux'
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
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
Projects and Labs
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 [email protected] Do cat /var/spool/mail/ [email protected] 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!
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
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 – 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 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 If you have problem with Kmail you may need to reinstall
Kmail