Web server administration chap08

Web Server Administration Chapter Providing E-mail Services Overview     Understand the e-mail environment Understand e-mail protocols Install and administer Microsoft Exchange 2000 Install and administer sendmail for Linux 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    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   Instant messaging Unified messaging platform    Chat service URL addressing   Single inbox for e-mail, voicemail, fax Use a single URL to access stored data Audio and video conferencing 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  MTA (Mail Transfer Agent)    MUA (Mail User Agent)    Accepts e-mail from clients and sends email to another MTA for storage Exchange 2000, sendmail E-mail client Outlook, KMail MDA (Mail Delivery Agent)   Delivers e-mail from server to MUA Exchange 2000, imap-2001 E-mail System Terminology  Masquerading   Relaying    Replace actual host name with domain name 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  SMTP (Simple Mail Transfer Protocol)   POP3 (Post Office Protocol)    To send e-mail messages 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  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 10 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 14 Sample POP3 SessionMajor Components USER cbranco +OK PASS pass +OK User successfully logged on LIST +OK 404 404 RETR +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 +OK QUIT 15 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 16 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 17 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 is required 18 Administering Exchange 2000  Messag e Deliver y Default s 19 Administering Exchange Users   When you add a user, you have the option to create a mailbox By default, the email name is the same as the user name but you can change it 20 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 21 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 22 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' 23 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 24 Configuring E-mail ClientsTypical Information Required     SMTP server IP address Your e-mail address Your e-mail password POP3 or IMAP4 server IP address 25 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 26 Web-based E-mail ClientsAdvantages       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 27 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 28 ... Information Required     SMTP server IP address Your e-mail address Your e-mail password POP3 or IMAP4 server IP address 25 Web- based E-mail Clients    Web- based e-mail clients allow you... To retrieve e-mail E-mail stays on the server You can create folders on server to store e-mail Understanding SMTP  The commands are processed by the SMTP server Command Purpose HELO Identifies... 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 26 Web- based E-mail ClientsAdvantages