Linux Email by Rusenko, David, McDonald, Alistair, Taylor, Carl -- Read -- Imperial Library of Trantor

Index

Linux E-mail

Linux E-mail Credits About the Authors About the Reviewers Preface

What this book covers Who this book is for Conventions Reader feedback Customer support

Errata Piracy Questions

1. Linux and E-mail Basics

Why manage your own e-mail server What you need to host an e-mail server Sizing the hardware of your e-mail server Main e-mail protocols: SMTP, POP, and IMAP

Overview POP protocol IMAP protocol The SMTP protocol

E-mail and DNS

DNS record types used by e-mail applications

Backup mail servers Summary

2. Setting up Postfix

Introduction to Postfix

What is Postfix Postfix architecture: An overview

New message arrival Scheduling message deliveries Message delivery Supporting programs

Installation and basic configuration

Choosing the Postfix version Installing from a package Installing from source code The Postfix configuration

main.cf master.cf Lookup tables

Getting Postfix up and running

Domains and hostnames Indirect mail delivery through your ISP Choosing network interfaces Choosing mailbox format for local deliveries Error reporting Other useful configuration parameters Starting Postfix and sending the first message

Stopping spam and other unwanted messages

Postfix's anti-spam methods: An overview Understanding SMTP restrictions

Access maps Access map examples Implementing new policies

Using DNS blacklists

Choosing DNS blacklists

Stopping messages based on content

Configuring header and body checks Header and body checks examples Caveats

Virtual alias domains and local aliases

Virtual alias domains

Many virtual alias domains mapping to one local domain One virtual alias domain mapping to many local domains Group addresses Introducing MySQL lookups

Local aliases

Command deliveries

Common pitfalls Other address rewriting mechanisms

Troubleshooting Postfix problems

Reading and interpreting the log files

Message queue ID SMTP submission and local delivery Local submission and SMTP delivery Connection problems upon SMTP delivery Getting more detailed log messages

Troubleshooting lookup tables with Postmap Getting help from the Postfix mailing list

Summary

3. Incoming Mail with POP and IMAP

Choosing between POP and IMAP Downloading and installing Courier-IMAP

Installing Courier-IMAP from a distribution repository Installing Courier-IMAP from RPM Installing Courier-IMAP using the Debian package format Installing Courier-IMAP from source

Prerequisites Building the Courier Authentication Library Configuring the Courier Authentication Library Resolving errors

Building Courier-IMAP

Handling errors

Using POP3

Configuring Courier-IMAP for POP3 Testing the POP3 Service Retrieving E-mail via POP3 with Windows Live Mail

Using IMAP

Configuring Courier for IMAP Testing the IMAP service Retrieving mail via IMAP with Mozilla Thunderbird

Summary

4. Providing Webmail Access

The webmail solution

The benefits

Easy and quick access Easy remote access No need to maintain clients Configuring mail server interface via the user interface Possible security benefits

The disadvantages

Performance Compatibility with large e-mail volumes Compatibility with e-mail attachments Security issues

The SquirrelMail webmail package SquirrelMail installation and configuration

Prerequisites to installation

Basic requirements

Installing Apache2 PHP

Perl Review configuration

Installing SquirrelMail

Source installation

Configuring SquirrelMail

SquirrelMail plugins

Installing plugins Example plugin installation

Downloading and unpacking the plugin Performing custom installation Enabling the plugin in conf.pl

Useful plugins

Securing SquirrelMail Summary

5. Securing Your Installation

Configuring Postfix network maps

SMTP-after-POP Virtual Private Networks SMTP Authentication Static IP ranges

Generic relay rules Explicit relay rules

Dynamic IP ranges

Cyrus SASL

SASL layers

Authentication interface Mechanism Method Password verification service

Installing Cyrus SASL Configuring Cyrus SASL

Selecting a password verification service Choosing a log level Choosing valid mechanisms

saslauthd

Using an IMAP server as authentication backend Using an LDAP server as authentication backend Using the local user accounts Using PAM

auxprop

Configuring the sasldb plugin Configuring the sql plugin

authdaemond

Setting the authdaemond password verification service Configuring the authdaemond socket path

Testing Cyrus SASL authentication Configuring Postfix SMTP AUTH

Preparing the configuration Enabling SMTP AUTH Setting the security policy Including broken clients

Testing SMTP AUTH Enabling relaying for authenticated clients Securing plaintext mechanisms

Enabling Transport Layer Security Configuring security policy

Dictionary attacks

Recipient maps

Checking local domain recipients Checking relay domain recipients

Rate-limiting connections

Summary

6. Getting Started with Procmail

Introduction to Procmail

Who wrote it and when

How can a filtering system help me?

Potential uses of mail filtering

Filtering and sorting mail Forwarding mail Processing the mail in an application Acknowledgements and out of office/vacation replies

File locking and integrity What Procmail is not suitable for

Downloading and installing Procmail

Installing via a package manager Installing from source Installation options/considerations

Individual installation System-wide installation

Integration with Postfix for system-wide delivery

Creating an alias for system accounts Adding Procmail to the Postfix configuration Postfix-provided environment variables

Basic operations

Configuration file

File format Configuration file dissection

Analyzing a simple rule

The rule structure

Variable analysis Rule analysis

Creating and testing a rule

A "hello world" example Creating rc.testing Performing static testing of the script Configuring Procmail to process rc.testing Testing the setup

Configuration debugging

Checking for typos in the scripts Looking at the log file for error messages Checking file and directory permissions Turning on Full Logging Taking steps to avoid disasters

Understanding e-mail structure

Message body E-mail headers Header structure Official definitions for headers

Example rule sets

From header Return-Path Header

Filtering by Return-Path

To and Cc headers

Filtering by To or Cc

Subject header

Filtering by subject

System-wide rules

Removing executables Large e-mails

Summary

7. Advanced Procmail

Delivering and non-delivering recipes

Non-delivering example

Formail Advanced recipe analysis

Adding comments Assigning variables

Performing substitutions

Assigning variable with default values Assigning command output to variables

Pseudo-variables

Mailbox variables Program variables System interaction variables Logging variables Procmail's state variables Message content variables Locking variables Error-handling variables Miscellaneous variables Printing Procmail variables

Recipes

Colon line

Locking

Automatic locking Enforced locking No locking

Flags

Default flags Scope of matching: HB Scope of action: hb Flow control: aAeEc Case sensitivity: D Execution mode: fwWir

Conditions

Applying a rule unconditionally Tests with regular expressions Testing the size of a message part Testing the exit code of an external program Negation Variable substitution in conditions

Action line

Forwarding to other addresses Feeding to a shell or command pipeline Saving to a folder Compound recipes

Regular expressions

Introduction to regular expressions

The dot Quantifier operation The asterisk The plus sign Restrictive matches using parentheses Creating a simple spam filter Character classes Start of line End of Line

Further reading ^TO and ^TO_ ^FROM_MAILER ^FROM_DAEMON

Advanced recipes

Creating a vacation auto reply Organizing mail by date Informing users about large mail

Procmail Module Library Putting it all together

Creating a structure to base your own rules upon

Rc.system Rc.lists Rc.killspam Rc.vacation Rc.largefiles Rc.viruses Rc.spamfilter

Summary

8. Busting Spam with SpamAssassin

Why filter e-mail

Spam is a moving target Spam filtering options

Introduction to SpamAssassin Downloading and installing SpamAssassin

Using CPAN

Configuring CPAN

Installing SpamAssassin using CPAN Using the rpmbuild utility Using pre-built RPMs Testing the installation

Modified e-mails

Using SpamAssassin

Using SpamAssassin with Procmail

Global procmailrc file Using SpamAssassin on a per-user basis

Using SpamAssassin as a daemon with Postfix Using SpamAssassin with amavisd-new

Installing amavisd-new from package Installation prerequisites Installing from source Creating a user account for amavisd-new Configuring amavisd-new Configuring Postfix to run amavisd-new

Configuring e-mail clients

Microsoft Outlook Microsoft Outlook Express Mozilla Thunderbird

Customizing SpamAssassin

Reasons to customize Rules and scores Altering rule scores Using other rulesets Whitelists and blacklists Bayesian filtering

Other SpamAssassin features Summary

9. Antivirus Protection

Introduction to ClamAV Document types supported Downloading and installing ClamAV

Adding a new system user and group Installing from a package Installing from source code

Requirements Building and installing Quick test

Editing the config files

clamd

Examining the sample config file

freshclam

Closest mirrors Examining the sample config file

File permissions

Post installation testing

EICAR test virus Testing clamscan Testing clamd Testing freshclam

Introduction to ClamSMTP

Building and installing Configuring into Postfix Configuring clamSMTP

Examining the sample config file

Testing e-mail filtering

Testing mail-borne virus filtering Thorough e-mail-borne testing

Automating update of virus data

Setting up auto updating

Automating startup and shutdown

ClamSMTP ClamAV

Monitoring log files Disinfecting files Summary

10. Backing Up Your System

Backup options

RAID Image backups File system backups Ad hoc backups

What to back up

System inventory Obtaining a list of installed software System configuration files Authentication data The users' mailboxes Log files The mail queue

What not to back up Backing up users' e-mail

Mail storage Using dump

Full dump Incremental dumps

Using restore

Interactive restore Non-interactive restore across the network

Backing up configurations and logs

Transferring configurations and logs to backup media Restoring the configuration

Automating backups

Backup script Adding crontab entries

Verifying restoration procedures Summary

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