sendmail Cookbook Craig Hunt O'REILLY' Beijing Cambridge Farnham Koln Paris Sebastopol Taipei Tokyo

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1 sendmail Cookbook Craig Hunt O'REILLY' Beijing Cambridge Farnham Koln Paris Sebastopol Taipei Tokyo

2 Table of Contents Preface xi 1. Getting Started Downloading the Latest Release Installing sendmail Compiling sendmail to Use LDAP Adding the regex Map Type to sendmail Compiling sendmail with SASL Support Compiling sendmail with STARTTLS Support Compiling in STARTTLS File Paths Building a sendmail Configuration Testing a New Configuration Logging sendmail Delivery and Forwarding Accepting Mail for Other Hosts * Fixing the AliasO Missing Map Error and Creating Simple Aliases Reading Aliases via LDAP Configuring Red Hat 7.3 to Read Aliases from a NIS Server Configuring Solaris 8 to Read Aliases from a NIS Server Forwarding to an External Address Creating Mailing Lists Migrating Ex-Users to New Addresses Delivering Mail to a Program Using Program Names in Mailing Lists Allowing Nonlogin Users to Forward to Programs Fixing a.forward Loop Enabling the User Database ' 71 vii

9 Testing a New Configuration 29 1.10 Logging sendmail 34 2. Delivery and Forwarding 37 2.1 Accepting Mail for Other Hosts * 39 2.

3 3. Relaying Passing All Mail to a Relay Passing Outbound Mail to a Relay Passing Local Mail to a Mail Hub Passing Apparently Local Mail to a Relay, Passing UUCP Mail to a Relay Relaying Mail for All Hosts in a Domain Relaying Mail for Individual Hosts Configuring Relaying on a Mail Exchanger Loading Class $=R via LDAP Relaying Only Outbound Mail Masquerading Adding Domains to All Sender Addresses Masquerading the Sender Hostname Eliminating Masquerading for the Local Mailer Forcing Masquerading of Local Mail Masquerading Recipient Addresses Masquerading at the Relay Host Limiting Masquerading Masquerading All Hosts in a Domain Masquerading Most of the Hosts in a Domain Masquerading the Envelope Address Rewriting the From Address with the genericstable Rewriting Sender Addresses for an Entire Domain Masquerading with LDAP Reading the genericstable via LDAP Routing Mail Routing Mail to Special Purpose Mailers Sending Error Messages from the mailertable Disabling MX Processing to Avoid Loops Routing Mail for Local Delivery Reading the mailertable via LDAP Routing Mail for Individual Virtual Hosts ' Routing Mail for Entire Virtual Domains Reading the virtusertable via LDAP Routing Mail with LDAP Using LDAP Routing with Masquerading 193 viii I Table of Contents

9 Loading Class $=R via LDAP 96 3.10 Relaying Only Outbound Mail 100 4. Masquerading 103 4.1 Adding Domains to All Sender Addresses 105 4.2 Masquerading the Sender Hostname 107 4.

4 6. Controlling Spam Blocking Spam with the access Database Preventing Local Users from Replying to Spammers Reading the access Database via LDAP Using a DNS Blackhole List Service Building Your Own DNS Blackhole List Whitelisting Blacklisted Sites Filtering Local Mail with procmail Filtering Outbound Mail with procmail Invoking Special Header Processing Using Regular Expressions in sendmail Identifying Local Problem Users Using MILTER Bypassing Spam Checks Enabling Spam Checks on a Per-User Basis Authenticating with AUTH Offering AUTH Authentication Authenticating with AUTH Storing AUTH Credentials in the authinfo File Limiting Advertised Authentication Mechanisms Using AUTH to Permit Relaying Controlling the AUTH= Parameter Avoiding Double Encryption Requiring Authentication Selectively Requiring Authentication Securing the Mail Transport Building a Private Certificate Authority Creating a Certificate Request Signing a Certificate Request Configuring sendmail for STARTTLS Relaying Based on the CA Relaying Based on the Certificate Subject Requiring Outbound Encryption Requiring Inbound Encryption Requiring a Verified Certificate Requiring TLS for a Recipient 308 Table of Contents ix

8 Filtering Outbound Mail with procmail 226 6.9 Invoking Special Header Processing 229 6.10 Using Regular Expressions in sendmail 231 6.11 Identifying Local Problem Users 234 6.12 Using MILTER 237 6.

5 8.11 Refusing STARTTLS Service Selectively Advertising STARTTLS Requesting Client Certificates Managing the Queue Creating Multiple Queues Using qf, df, and xf Subdirectories Defining Queue Groups Assigning Recipients to Specific Queues Using Persistent Queue Runners Using a Queue Server Setting Protocol Timers Securing sendmail Limiting the Number of sendmail Servers Limiting the Number of Network Accessible Servers Updating to Close Security Holes Patching to Close Security Holes Disabling Delivery to Programs Controlling Delivery to Programs Disabling Delivery to Files Bypassing User.forward Files Controlling Delivery to Files Running sendmail Non-Set-User-ID root Setting a Safe Default User ID Defining Trusted Users Identifying the sendmail Administrator Limiting the SMTP Command Set Requiring a Valid HELO Restricting Command-Line Options Denying DoS Attacks 372 Index 375 x Table of Contents

7 Setting Protocol Timers 335 10. Securing sendmail 338 10.1 Limiting the Number of sendmail Servers 339 10.2 Limiting the Number of Network Accessible Servers 342 10.

CipherMail Gateway Quick Setup Guide

CIPHERMAIL EMAIL ENCRYPTION CipherMail Gateway Quick Setup Guide October 10, 2015, Rev: 9537 Copyright 2015, ciphermail.com. CONTENTS CONTENTS Contents 1 Introduction 4 2 Typical setups 4 2.1 Direct delivery............................