1. Chapter 1 Introduction

2. Chapter 2 How Internet Mail Works

   1. Different Types of MTA

   2. Internet Message Standards

   3. RFC 822 Message Format

   4. The Message “On the Wire”

   5. Summary of the SMTP Protocol

   6. Forgery

   7. Authentication and Encryption

   8. Routing a Message

   9. Checking Incoming Mail

   10. Overview of the DNS

   11. DNS Records Used for Mail Routing

   12. Related DNS Records

   13. Common DNS Errors

   14. Role of the Postmaster

3. Chapter 3 Exim Overview

   1. Exim Philosophy

   2. Exim’s Queue

   3. Receiving and Delivering Messages

   4. Exim Processes

   5. Coordination Between Processes

   6. How Exim Is Configured

   7. How Exim Delivers Messages

   8. Local and Remote Addresses

   9. Processing an Address

   10. A Simple Example

   11. Complications While Directing and Routing

   12. Complications During Delivery

   13. Complications After Delivery

   14. Use of Transports by Directors and Routers

4. Chapter 4 Exim Operations Overview

   1. How Exim Identifies Messages

   2. Watching Exim at Work

   3. The Runtime Configuration File

   4. The Default Qualification Domain

   5. Handling Frozen Bounce Messages

   6. Reducing Activity at High Load

   7. Limiting Message Sizes

   8. Parallel Remote Delivery

   9. Controlling the Number of Delivery Processes

   10. Large Message Queues

   11. Large Installations

5. Chapter 5 Extending the Delivery Configuration

   1. Multiple Local Domains

   2. Virtual Domains

   3. Mailing Lists

   4. Using an External Local Delivery Agent

   5. Multiple User Addresses

   6. Mixed Local/Remote Domains

   7. Delivering to UUCP

   8. Ignoring the Local Part in Local Deliveries

   9. Handling Local Parts in a Case-Sensitive Manner

   10. Scanning Messages for Viruses

   11. Modifying Message Bodies

6. Chapter 6 Options Common to Directors and Routers

   1. Conditional Running of Routers and Directors

   2. Changing a Driver’s Successful Outcome

   3. Adding Data for Use by Transports

   4. Debugging Directors and Routers

   5. Summary of Director/Router Generic Options

7. Chapter 7 The Directors

   1. Conditional Running of Directors

   2. Optimizing Single-Level Aliasing

   3. Adding Data for Use by Transports

   4. The aliasfile and forwardfile Directors

   5. The aliasfile Director

   6. The forwardfile Director

   7. The localuser Director

   8. The smartuser Director

8. Chapter 8 The Routers

   1. Timeouts While Routing

   2. Domains That Route to the Local Host

   3. The lookuphost Router

   4. The domainlist Router

   5. The ipliteral Router

   6. The queryprogram Router

9. Chapter 9 The Transports

   1. Options Common to All Transports

   2. The smtp Transport

   3. Environment for Local Transports

   4. Options Common to the appendfile and pipe Transports

   5. The appendfile Transport

   6. The pipe Transport

   7. The lmtp Transport

   8. The autoreply Transport

10. Chapter 10 Message Filtering

    1. Examples of Filter Commands

    2. Filtering Compared with an External Delivery Agent

    3. Setting Up a User Filter

    4. Setting Up a System Filter

    5. Testing Filter Files

    6. Format of Filter Files

    7. Significant Actions

    8. Filter Commands

    9. The add Command

    10. Delivery Commands

    11. Mail Commands

    12. Logging Commands

    13. The testprint Command

    14. The finish Command

    15. Obeying Filter Commands Conditionally

    16. Additional Features for System Filters

11. Chapter 11 Shared Data and Exim Processes

    1. Message Files

    2. Locking Message Files

    3. Hints Files

    4. Log Files

    5. User and Group IDs for Exim Processes

    6. Process Relationships

    7. The Daemon Process

    8. Reception Processes

    9. Queue Runner Processes

    10. Delivery Processes

    11. Summary of Message Handling Process Types

    12. Other Types of Process

12. Chapter 12 Delivery Errors and Retrying

    1. Retrying After Errors

    2. Remote Delivery Errors

    3. Local Delivery Errors

    4. Routing and Directing Errors

    5. Retry Rules

    6. Computing Retry Times

    7. Using Retry Times

    8. Retry Rule Examples

    9. Timeout of Retry Data

    10. Long-Term Failures

    11. Ultimate Address Timeout

    12. Intermittently Connected Hosts

13. Chapter 13 Message Reception and Policy Controls

    1. Message Sources

    2. Message Size Control

    3. Messages from Local Processes

    4. Unqualified Addresses from Remote Hosts

    5. Checking a Remote Host

    6. Checking Remote Sender Addresses

    7. Checking Recipient Addresses

    8. Checking Header Line Syntax

    9. Relay Control

    10. Customizing Prohibition Messages

    11. Incoming Message Processing

14. Chapter 14 Rewriting Addresses

    1. Automatic Rewriting

    2. Configured Rewriting

    3. Rewriting Rules

    4. Rewriting Patterns

    5. Rewriting Flags

    6. A Further Rewriting Example

    7. Testing Rewriting Rules

15. Chapter 15 Authentication, Encryption, and Other SMTP Processing

    1. SMTP Authentication

    2. Encrypted SMTP Connections

    3. SMTP over TCP/IP

    4. Local SMTP

    5. Batched SMTP

16. Chapter 16 File and Database Lookups

    1. Single-Key Lookup Types

    2. Query-Style Lookup Types

    3. Quoting Lookup Data

    4. NIS+

    5. LDAP

    6. MySQL and PostgreSQL

    7. DNS Lookups

    8. Implicit Keys in Query-Style Lookups

    9. Temporary Errors in Lookups

    10. Default Values in Single-Key Lookups

    11. Partial Matching in Single-Key Lookups

    12. Lookup Caching

17. Chapter 17 String Expansion

    1. Variable Substitution

    2. Header Insertion

    3. Operations on Substrings

    4. Character Translation

    5. Text Substitution

    6. Conditional Expansion

    7. Lookups in Expansion Strings

    8. Extracting Fields from Substrings

    9. IP Address Masking

    10. Quoting

    11. Reexpansion

    12. Running Embedded Perl

    13. Testing String Expansions

18. Chapter 18 Domain, Host, and Address Lists

    1. Negative Items in Lists

    2. List Items in Files

    3. Lookup Items in Lists

    4. Domain Lists

    5. Host Lists

    6. Address Lists

19. Chapter 19 Miscellany

    1. Security Issues

    2. Privileged Users

    3. RFC Conformance

    4. Timestamps

    5. Checking Spool Space

    6. Control of DNS Lookups

    7. Bounce Message Handling

    8. Miscellaneous Controls

20. Chapter 20 Command-Line Interface to Exim

    1. Input Mode Control

    2. Additional Message Data

    3. Immediate Delivery Control

    4. Error Routing

    5. Queue Runner Processes

    6. Configuration Overrides

    7. Watching Exim’s Queue

    8. Message Control

    9. Testing Options

    10. Options for Debugging

    11. Terminating the Options

    12. Embedded Perl Options

    13. Compatibility with Sendmail

    14. Calling Exim by Different Names

21. Chapter 21 Administering Exim

    1. Log Files

    2. Log Destination Control

    3. Format of Main Log Entries

    4. Cycling Log Files

    5. Extracting Information from Log Files

    6. Watching What Exim is Doing

    7. The Exim Monitor

    8. Maintaining Alias and Other Datafiles

    9. Hints Database Maintenance

    10. Mailbox Maintenance

22. Chapter 22 Building and Installing Exim

    1. Prerequisites

    2. Fetching and Unpacking the Source

    3. Configuration for Building

    4. The Building Process

    5. Installing Exim

    6. Testing Before Turning On

    7. Turning Exim On

    8. Installing Documentation in Info Format

    9. Upgrading to a New Release

1. Appendix Summary of String Expansion

   1. Expansion Items

   2. Expansion Conditions

   3. Expansion Variables

2. Appendix Regular Expressions

   1. Testing Regular Expressions

   2. Metacharacters

   3. Backslash

   4. Changing Matching Options

   5. Circumflex and Dollar

   6. Dot (Period, Full Stop)

   7. Square Brackets

   8. POSIX Character Classes

   9. Vertical Bar

   10. Subpatterns

   11. Repetition

   12. Back References

   13. Assertions

   14. Once-Only Subpatterns

   15. Conditional Subpatterns

   16. Comments

   17. Recursive Patterns

   18. Performance

3. Colophon

Our look is the result of reader comments, our own experimentation, and feedback from distribution channels. Distinctive covers complement our distinctive approach to technical topics, breathing personality and life into potentially dry subjects. The animal on the cover of Exim: The Mail Transfer Agent is an aye-aye. The aye-aye is part of the order of primates, and in fact is part of the lemur group. Native to Madagascar, they are considered one of the strangest looking primates, and not very much is known about them. A full-grown adult is about the size of a raccoon. Its features include large round ears, black fur with white spots, a flat nose, and big round eyes. Two very distinctive characteristics of the aye-aye are its incisor teeth, which never stop growing, and its long, spindly fingers, of which the middle finger is the longest. Both of these traits are used as tools in hunting food. The aye-aye lives mostly on bug larvae and fruit; it often uses its teeth to break open dead tree bark, then uses its long middle finger to reach inside and take hold of the bugs.

The aye-aye is completely nocturnal, and lives mostly in trees in the forest. Unfortunately, it is dangerously close to extinction. One reason for this is that its natural habitat, the rain forest, is gradually being destroyed for resources. Due to this loss of its food source, the aye-aye has had to forage for food in other areas, and often steals from local farms. For this reason, it is killed as a pest. Also, in parts of Madagascar, there is a superstition that the aye-aye is a harbinger of bad luck and death; therefore, it is often killed on sight. However, steps are being taken to ensure the safety of the species, such as breeding some in captivity and declaring certain areas of the forest as protected. Mary Brady was the production editor and proofreader and Mark Nigara was the copyeditor for Exim: The Mail Transfer Agent. Jane Ellin and Claire Cloutier provided quality control. Ann Schirmer, Gabe Weiss, and Lucy Muellner provided production assistance. Nancy Crumpton wrote the index.

Ellie Volckhausen designed the cover of this book, based on a series design by Edie Freedman. The cover image is a 19th-century engraving from the Dover Pictorial Archive. Erica Corwell produced the cover layout with QuarkXPress 4.1 using Adobe's ITC Garamond font.

David Futato designed the interior layout based on a series design by Nancy Priest. The print version of this book was created by translating the DocBook XML markup of its source files into a set of gtroff macros using a filter developed at O'Reilly & Associates by Norman Walsh. Steve Talbott designed and wrote the underlying macro set on the basis of the GNU troff s macros; Lenny Muellner adapted them to XML and implemented the book design. The GNU groff text formatter Version 1.11.1 was used to generate PostScript output. The text and heading fonts are ITC Garamond Light and Garamond Book; the code font is Constant Willison. The illustrations that appear in the book were produced by Robert Romano and Jessamyn Read using Macromedia FreeHand 9 and Adobe Photoshop 6. This colophon was written by Mary Brady.