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Web Server Administration

Web Server Administration . Chapter 8 Providing E-mail Services. Overview. Understand the e-mail environment Understand e-mail protocols Understand Web-based e-mail clients. Understanding the E-mail Environment. E-mail evolved from a variety of proprietary systems

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Web Server Administration

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  1. Web Server Administration Chapter 8 Providing E-mail Services

  2. Overview • Understand the e-mail environment • Understand e-mail protocols • Understand Web-based e-mail clients

  3. 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

  4. 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

  5. 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

  6. DNS configuration for technowidgets.com

  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. Terminology – Mail Agents

  9. 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

  10. 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

  11. Understanding SMTP • The commands are processed by the SMTP server

  12. Understanding SMTP • The SMTP headers add descriptive information

  13. 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 <CRLF>.<CRLF> This is a simple message . QUIT

  14. Attempted Relay (Spam) • 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@edswidgets.com 550 5.7.1 Unable to relay for edswidgets.com

  15. Understanding POP3 • More simplistic than IMAP4 • First step is to log on with user name and password • Usually login ID and Password are not encrypted – but this feature is available • List, read, download, delete e-mail

  16. Common POP3 commands

  17. 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

  18. 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

  19. Common IMAP4 commands

  20. 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

  21. Administering Exchange 2000 • Message Delivery Defaults

  22. 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

  23. 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

  24. 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

  25. 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'

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

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