Red Hat Linux 7 Unleashed

By William Ball

• Table of Contents
  • Copyright
  • About the Lead Authors
  • About the Contributing Authors
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • I. Red Hat Linux Installation and User Services
  • Chapter 1. Introduction to Red Hat Linux
  • Chapter 2. Installation of Your Red Hat System
  • Chapter 3. LILO and Other Boot Managers
  • Chapter 4. Configuring the X Window System, Version 11
  • Chapter 5. Window Managers
  • Chapter 6. Connecting to the Internet
  • Chapter 7. IRC, ICQ, and Chat Clients
  • Chapter 8. Using Multimedia and Graphics Clients
  • II. Configuring Services
  • Chapter 9. System Startup and Shutdown
  • Chapter 10. SMTP and Protocols
    • A Brief History of Internet Email Standards
    • SMTP and sendmail
    • POP
    • IMAP
    • Mail Retrieval
    • Summary
  • Chapter 11. FTP
  • Chapter 12. Apache Server
  • Chapter 13. Internet News
  • Chapter 14. Domain Name Service and Dynamic Host Configuration Protocol
  • Chapter 15. NIS: Network Information Service
  • Chapter 16. NFS: Network Filesystem
  • Chapter 17. Samba
  • III. System Administration and Management
  • Chapter 18. Linux Filesystems, Disks, and Other Devices
  • Chapter 19. Printing with Linux
  • Chapter 20. TCP/IP Network Management
  • Chapter 21. Linux System Administration
  • Chapter 22. Backup and Restore
  • Chapter 23. System Security
  • IV. Red Hat Development and Productivity
  • Chapter 24. Linux C/C++ Programming Tools
  • Chapter 25. Shell Scripting
  • Chapter 26. Automating Tasks
  • Chapter 27. Configuring and Building Kernels
  • Chapter 28. Emulators, Tools, and Window Clients
  • V. Appendixes
  • A. The Linux Documentation Project
  • B. Top Linux Commands and Utilities
  • C. The GNU General Public License
  • D. Red Hat Linux RPM Package Listings

Summary

In this chapter you learned how to install, set up, configure, and test sendmail, ipop3d, and imapd, as well as to retrieve your mail using Netscape and fetchmail. The key things to remember about this process follow:

• An MTA is a Mail Transfer Agent (which actually routes and delivers mail), and an MUA is a Mail User Agent (which is what the user uses to access mail after it has been delivered). sendmail is an MTA only.
• The Simple Mail Transfer Protocol (SMTP) is the actual protocol used to transfer mail. sendmail is a program that uses this protocol to communicate with other mail servers. Other mail servers don't need to run sendmail, but they do need to communicate via SMTP.
• sendmail does not deliver mail once it has reached the destination system. A special program that's local to the system, such as /bin/mail or /usr/bin/procmail, is used to perform the delivery functions.
• The aliases file can remap email addresses to other usernames, redirect mail to files, or pass on email messages to another program for processing. Remember to run the newaliases program every time you change the alias file.
• sendmail is a large program with a history of security problems. Hence, be sure to keep up with the security bulletins. The security section at http://www.lwn.net (Linux Weekly News) is worth checking regularly, as well as ftp://updates.redhat.com (or mirrors) for security updates to your particular distribution.
• Whenever a new version of sendmail is released, download it from ftp.sendmail.org and install it.
• The Post Office Protocol (POP) is a protocol for allowing client machines to connect to a mail server and transfer mail. POP is not responsible for delivering mail to other users or systems.
• Although POP isn't nearly as large or complex as sendmail, it does have the potential for security problems (as does any Internet-accessible service). Watch for security announcements and upgrade accordingly.
• APOP is the means by which the POP protocol accepts passwords in an encrypted format.
• The Internet Message Access Protocol (IMAP) is a protocol for allowing client machines to connect to a mail server and access your email without having to download all your waiting messages at once. It also allows easy remote access to email when you are constantly moving around, by allowing you to manipulate mail folders on your mail server.
• Netscape Messenger can be configured to talk to either a POP or an IMAP server quite easily.
• fetchmail is an alternative method to process your mail from either a POP or an IMAP server.
• fetchmail passes mail to your local Mail Transfer Agent (MTA) for processing—sendmail, for example.

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