Chapter 24. Email

Chapter 24. Email

24.1. Email Protocols
24.1.1. Mail Transport Protocols
24.1.2. Mail Access Protocols
24.2. Email Program Classifications
24.2.1. Mail Transport Agent
24.2.2. Mail Delivery Agent
24.2.3. Mail User Agent
24.3. Mail Transport Agents
24.3.1. Sendmail
24.3.2. Postfix
24.3.3. Fetchmail
24.4. Mail Transport Agent (MTA) Configuration
24.5. Mail Delivery Agents
24.5.1. Procmail Configuration
24.5.2. Procmail Recipes
24.6. Mail User Agents
24.6.1. Securing Communication
24.7. Additional Resources
24.7.1. Installed Documentation
24.7.2. Useful Websites
24.7.3. Related Books

The birth of electronic mail (email) occurred in the early 1960s. The mailbox was a file in a user's home directory that was readable only by that user. Primitive mail applications appended new text messages to the bottom of the file, making the user wade through the constantly growing file to find any particular message. This system was only capable of sending messages to users on the same system.

The first network transfer of an electronic mail message file took place in 1971 when a computer engineer named Ray Tomlinson sent a test message between two machines via ARPANET — the precursor to the Internet. Communication via email soon became very popular, comprising 75 percent of ARPANET's traffic in less than two years.

Today, email systems based on standardized network protocols have evolved into some of the most widely used services on the Internet. Red Hat Enterprise Linux offers many advanced applications to serve and access email.

This chapter reviews modern email protocols in use today and some of the programs designed to send and receive email.

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