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Postfix: The Definitive Guide

Name: Postfix: The Definitive Guide
Author: Kyle D. Dent
ISBN: 9780596002121

by Kyle D. Dent

December 2003

Beginner

278 pages

10h 47m

English

O'Reilly Media, Inc.

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Foreword
Preface
Audience
Organization
Conventions Used in This Book
Comments and Questions
Acknowledgments
1. Introduction
1.1. Postfix Origins and Philosophy
1.2. Email and the Internet
1.2.1. Email Components1.2.2. Major Email Protocols1.2.2.1. SMTP and email submission1.2.2.2. POP/IMAP and mailbox access

1.3. The Role of Postfix
1.4. Postfix Security
1.4.1. Modular Design1.4.2. Shells and Processes1.4.3. Security by Design
1.5. Additional Information and How to Obtain Postfix
2. Prerequisites
2.1. Unix Topics
2.1.1. Login Names and UID Numbers2.1.2. Pseudo-Accounts2.1.3. Standard Input/Standard Output2.1.4. The Superuser2.1.5. Command Prompts2.1.6. Long Lines2.1.7. ManPages
2.2. Email Topics
2.2.1. RFCs2.2.2. Email Agents2.2.3. The Postmaster2.2.4. Reject or Bounce2.2.5. Envelope Addresses and Message Headers2.2.6. Local Parts of Email Addresses2.2.7. Email Message Format2.2.7.1. RFC 2822 messages2.2.8. The SMTP Protocol
3. Postfix Architecture
3.1. Postfix Components
3.2. How Messages Enter the Postfix System
3.2.1. Local Email Submission3.2.2. Email from the Network3.2.3. Postfix Email Notifications3.2.4. Email Forwarding
3.3. The Postfix Queue
3.4. Mail Delivery
3.4.1. Local Delivery3.4.2. Virtual Alias Messages3.4.3. Virtual Mailbox Messages3.4.4. Relay Messages3.4.5. Other Messages3.4.6. Other Delivery Agents3.4.6.1. Delivery via LMTP3.4.6.2. Pipe delivery
3.5. Tracing a Message Through Postfix
4. General Configuration and Administration
4.1. Starting Postfix the First Time
4.2. Configuration Files
4.2.1. The main.cf Configuration File4.2.1.1. Line continuation4.2.1.2. Configuration variables4.2.1.3. Multiple values4.2.2. Lookup Tables4.2.2.1. Lookup table format4.2.2.2. Database formats4.2.2.3. Search order4.2.2.4. Lookup tables and simple lists4.2.2.5. Regular expression tables4.2.3. Other Formats4.2.4. Alias Files4.2.4.1. Locating aliases4.2.4.2. Building alias database files4.2.4.3. Alias file format4.2.4.4. Alias restrictions4.2.4.5. Important aliases
4.3. Important Configuration Considerations
4.3.1. Configuring Your MTA Identity4.3.1.1. myhostname and mydomain4.3.1.2. myorigin4.3.1.3. mydestination4.3.2. Relay Control4.3.2.1. Restricting relay access4.3.2.2. SMTP authentication4.3.2.3. Dynamic IP solutions4.3.2.4. Certificate authentication
4.4. Administration
4.4.1. Logging4.4.2. Starting, Stopping, and Reloading Postfix4.4.3. Running Postfix at System Startup4.4.3.1. Do it yourself4.4.4. Queue Management
4.5. master.cf
4.6. Receiving Limits
4.7. Rewriting Addresses
4.7.1. Canonical Addresses4.7.2. Masquerading Hostnames4.7.3. Relocated Users4.7.4. Unknown Users
4.8. chroot
4.9. Documentation
5. Queue Management
5.1. How qmgr Works
5.1.1. Deferred Mail5.1.2. Queue Scheduling5.1.3. Message Delivery5.1.4. Corrupt Messages5.1.5. Error Notifications
5.2. Queue Tools
5.2.1. Listing the Queue5.2.2. Deleting Messages5.2.3. Holding Messages5.2.4. Requeuing Messages5.2.5. Displaying Messages5.2.6. Flushing Messages
6. Email and DNS
6.1. DNS Overview
6.2. Email Routing
6.3. Postfix and DNS
6.3.1. DNS and Sending Mail6.3.1.1. Configuration options6.3.1.2. Reverse PTR records6.3.2. DNS and Receiving Mail
6.4. Common Problems
7. Local Delivery and POP/IMAP
7.1. Postfix Delivery Transports
7.2. Message Store Formats
7.2.1. The Mbox Format7.2.2. The Maildir Format7.2.3. Mbox Versus Maildir
7.3. Local Delivery
7.3.1. .forward Files7.3.2. Alias Deliveries7.3.3. Mailbox Delivery
7.4. POP and IMAP
7.4.1. POP Versus IMAP7.4.2. Postfix and POP/IMAP Servers
7.5. Local Mail Transfer Protocol
7.5.1. Postfix and Cyrus IMAP7.5.2. A Postfix and Cyrus IMAP Example
8. Hosting Multiple Domains
8.1. Shared Domains with System Accounts
8.2. Separate Domains with System Accounts
8.3. Separate Domains with Virtual Accounts
8.3.1. Mailbox File Ownership8.3.2. Virtual Aliases8.3.3. Catchall Addresses8.3.3.1. Virtual mailbox catchall8.3.3.2. Virtual alias catchall
8.4. Separate Message Store
8.5. Delivery to Commands
8.5.1. Configuring a Virtual Auto-Responder8.5.2. Configuring a Virtual Mailing List Manager
9. Mail Relaying
9.1. Backup MX
9.1.1. Relay Recipients9.1.2. Fast Flushing
9.2. Transport Maps
9.2.1. Postponing Mail Delivery9.2.1.1. Deferring mail relay9.2.1.2. Deferring delivery
9.3. Inbound Mail Gateway
9.4. Outbound Mail Relay
9.5. UUCP, Fax, and Other Deliveries
10. Mailing Lists
10.1. Simple Mailing Lists
10.1.1. Mailing-List Owners10.1.2. Separate List Files10.1.3. Additional Alias Files10.1.4. Creating a Simple Mailing List10.1.5. Testing Your List
10.2. Mailing-List Managers
10.2.1. Majordomo10.2.1.1. Creating a Majordomo list10.2.1.2. Potential problems10.2.2. Mailman10.2.2.1. Creating a Mailman list
11. Blocking Unsolicited Bulk Email
11.1. The Nature of Spam
11.2. The Problem of Spam
11.3. Open Relays
11.4. Spam Detection
11.4.1. Client-Based Spam Detection11.4.1.1. DNS-based blacklists11.4.2. Content-Based Spam Detection11.4.3. Detection Difficulties
11.5. Anti-Spam Actions
11.6. Postfix Configuration
11.7. Client-Detection Rules
11.7.1. The SMTP Conversation (Briefly)11.7.2. Listing Restrictions11.7.2.1. How restrictions work11.7.2.2. Testing new restrictions11.7.2.3. A simple example11.7.3. Restriction Definitions11.7.3.1. Access maps11.7.3.2. Other client-checking restrictions11.7.3.3. Strict syntax restrictions11.7.3.4. DNS restrictions11.7.3.5. Real-time blacklists11.7.3.6. Generic restrictions11.7.4. Tracing a Restriction List
11.8. Strict Syntax Parameters
11.9. Content-Checking
11.9.1. Content Checking Configuration11.9.2. Content Checking Actions11.9.3. Comparing Patterns
11.10. Customized Restriction Classes
11.10.1. Sample Restriction Classes
11.11. Postfix Anti-Spam Example
12. SASL Authentication
12.1. SASL Overview
12.1.1. Choosing an Authentication Mechanism12.1.2. Choosing an Authentication Framework
12.2. Postfix and SASL
12.3. Configuring Postfix for SASL
12.3.1. Specifying a Framework12.3.1.1. Unix passwords12.3.1.2. SASL passwords12.3.2. Configuring Postfix12.3.2.1. Enabling SASL12.3.2.2. Preventing sender spoofing12.3.2.3. Permitting authenticated users12.3.2.4. Specifying mechanisms12.3.3. Configuration Summary
12.4. Testing Your Authentication Configuration
12.5. SMTP Client Authentication
12.5.1. Procedure to Enable SMTP Client Authentication
13. Transport Layer Security
13.1. Postfix and TLS
13.2. TLS Certificates
13.2.1. Becoming a CA13.2.2. Generating Server Certificates13.2.3. Installing CA Certificates13.2.4. Postfix/TLS Configuration13.2.5. Postfix/TLS Configuration Summary13.2.6. Requiring Client-Side Certificates13.2.6.1. Creating client certificates13.2.6.2. Configuring client-side certificate authentication13.2.7. Configuring TLS/SMTP Client
14. Content Filtering
14.1. Command-Based Filtering
14.1.1. Configuration
14.2. Daemon-Based Filtering
14.2.1. Configuration14.2.1.1. Creating a pseudoaccount14.2.1.2. Installing a content filter14.2.1.3. Configuring additional Postfix components14.2.1.4. Turning on filtering14.2.2. Daemon-Based Filter Example
14.3. Other Considerations
15. External Databases
15.1. MySQL
15.1.1. MySQL Configuration15.1.1.1. MySQL parameters15.1.2. MySQL Example15.1.2.1. Configuring local_recipient_maps15.1.2.2. Configuring alias_maps15.1.2.3. Configuring virtual domains
15.2. LDAP
15.2.1. LDAP Configuration15.2.2. LDAP Example15.2.2.1. Configuring local_recipient_maps15.2.2.2. Configuring transport_maps
A. Configuration Parameters
A.1. Postfix Parameter Reference
B. Postfix Commands
C. Compiling and Installing Postfix
C.1. Obtaining Postfix
C.2. Postfix Compiling Primer
C.2.1. Compiler OptionsC.2.2. Linker Options
C.3. Building Postfix
C.3.1. Customizing Your BuildC.3.2. Modifying Postfix Defaults
C.4. Installation
C.4.1. Upgrading
C.5. Compiling Add-on Packages
C.5.1. Cyrus SASLC.5.2. TLSC.5.3. MySQLC.5.4. LDAP
C.6. Common Problems
C.6.1. Compile TimeC.6.2. Runtime
C.7. Wrapping Things Up
D. Frequently Asked Questions
Index
About the Author
Colophon
Copyright

Content preview from Postfix: The Definitive Guide

Rewriting Addresses

Postfix tries to make sense of addresses in email and writes them using the standard RFC 2822 format. Certain address rewriting occurs automatically.

You saw earlier in the chapter how Postfix appends myorigin to a local name that has no domain part. Postfix also appends the value of mydomain to addresses that include only the host portion without the domain name. This fixes addresses that look like kdent@host so they become kdent@host.example.com.

Postfix’s expansion of incomplete email addresses is sometimes the source of confusion for end users. If your system is hosting the domain example.com and receives an email message where the From: message header contains an incomplete address like:

From: Marketing
To: kdent@example.com

Postfix performs its normal repairs, and the message header becomes:

From: Marketing@example.com
To: kdent@example.com

Incomplete addresses, such as in this example, are often employed by spammers. When naive users see the adjusted address, they assume that the spam originated on your server. It is possible to configure Postfix so that it doesn’t append your domain. You probably don’t want to do so unless your mail system is used strictly as a mail gateway and no messages are sent from the machine itself. Many applications expect RFC 2822 conforming addresses, and you may run into problems if your addresses are not complete.

To prevent Postfix from appending the domain in myorigin or mydomain to partial addresses, ...

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Postfix: The Definitive Guide

by Kyle D. Dent

Rewriting Addresses

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.