System Administration Guide: Network Services

Chapter 12 Mail Services (Overview)

Setting up and maintaining an electronic mail service involves complex tasks that are critical to the daily operation of your network. As a network administrator, you might need to expand an existing mail service. Alternately, you might need to set up a mail service on a new network or a subnet. The chapters on mail services can help you plan and set up a mail service for your network. This chapter provides links to descriptions of new features in sendmail, as well as a list of other sources of information. The chapter also provides overviews of the software and hardware components that are required to establish a mail service.

See Chapter 13, Mail Services (Tasks) for procedural information about how to set up and administer mail services. For details, refer to Task Map for Mail Services.

See Chapter 14, Mail Services (Reference) for a more detailed description of the components of mail services. This chapter also describes the mail service programs and files, the mail routing process, the interactions of sendmail with name services, and the features in version 8.13 of sendmail. See Changes in Version 8.13 of sendmail.

What's New With Mail Services

This section provides information about new features in various Solaris releases.

Changes in this Release

The following changes have been made in the Solaris 10 7/10 release release:

Changes in the Solaris 10 1/06 Release

Starting in the Solaris 10 1/06 release, sendmail supports SMTP using Transport Layer Security (TLS). For more information, see the following:

For a complete list of features in the Solaris 10 1/06 release, see Oracle Solaris 10 9/10 What’s New.

Changes in the Solaris 10 Release

Starting in the Solaris 10 release, sendmail version 8.13 is the default. For information about version 8.13 and other changes, see the following:

Additionally, the mail service is managed by the Service Management Facility. Administrative actions on this service, such as enabling, disabling, or restarting, can be performed by using the svcadm command. The service's status can be queried by using the svcs command. For more information about the Service Management Facility, see the smf(5) man page and Chapter 18, Managing Services (Overview), in System Administration Guide: Basic Administration.

Other sendmail Information Sources

The following is a list of additional information sources about sendmail.

Introduction to the Components of Mail Services

Many software and hardware components are required to establish a mail service. The following sections give a quick introduction to these components. These sections also provide some of the terms that are used to describe the components.

The first section, Overview of the Software Components, defines the terms that are used when discussing the software parts of the mail delivery system. The next section, Overview of the Hardware Components, focuses on the functions of the hardware systems in a mail configuration.

Overview of the Software Components

The following table introduces some of the software components of a mail system. Refer to Software Components for a complete description of all of the software components.



.forward files

Files that you can set up in a user's home directory to redirect mail or to send mail to a program automatically 


A file on a mail server that is the final destination for email messages 

mail addresses 

Address that contains the name of the recipient and the system to which a mail message is delivered 

mail aliases 

An alternate name that is used in a mail address 

mail queue 

A collection of mail messages that needs to be processed by the mail server 


A special mail alias that is used to report problems and to ask questions about the mail service 

sendmail configuration file 

A file that contains all the information necessary for mail routing 

Overview of the Hardware Components

A mail configuration requires three elements, which you can combine on the same system or provide in separate systems.

If users are to communicate with networks outside your domain, you must also add a fourth element, a mail gateway.

Figure 12–1 shows a typical electronic mail configuration, using the three basic mail elements plus a mail gateway.

Figure 12–1 Typical Electronic Mail Configuration

Diagram shows the dependencies between a mail gateway,
a mail host, mail servers, mailboxes, clients.

Each element is described in detail in Hardware Components.