CHAPTER 2
Planning Mail Services

Local Mail Only

Local Mail and a uucp Connection

One Domain, Two Networks, and a Router

Two Domains and a Gateway

This chapter describes four basic mail configurations and briefly outlines the tasks required to set up each configuration. You may find the following sections useful if you need to set up a new mail system or are expanding an existing one. The configurations start with the most basic case (mail completely local, no connection to the outside world) and increase in complexity to a two-domain configuration with a gateway. More complex systems are beyond the scope of this book.

To set up a mail system, regardless of its configuration, you need these elements:

•  A sendmail.cf configuration file on each system

•  Alias files with an alias for each user to point to the place where mail is to be delivered

•  A mailbox to store (or spool) mail files for each user

•  A postmaster alias for the person who administers mail services

See Chapter 3, "Setting Up and Administering Mail Services," for detailed information on how to set up these elements.

How you set up the configuration file and the alias file and where you put the mailboxes depend on the configuration you choose.

Local Mail Only

The simplest mail configuration, shown in Figure 2-1, is one mail server with a number of workstations connected to it. Mail is completely local. One system is both the mail server (providing mail spooling for client mailboxes) and the mailhost. Mail addresses are parsed using the /etc/mail/aliases files. No naming service, such as NIS, NIS+, or DNS, is used.

Figure 2-1  Local mail configuration.

To set up this kind of local mail configuration (assuming that the mail clients mount their mail files from /var/mail on the mailhost), you need the following:

•  The default sendmail.cf file in the /etc/mail directory on each system (no editing required).

•  A server designated as the mailhost. (Add mailhost to the /etc/hosts file on the mailhost.)

•  The mailhost IP address line added to the /etc/hosts file of each mail client.

•  Entries in each mail client's /etc/vfstab file to mount the /var/mail directory when mailboxes are located on the mail server.

See Chapter 3 for detailed information on how to set up mail services.

Local Mail and a uucp Connection

The most common mail configuration in a small network can be seen in Figure 2-2. One system connects the mail server, the mailhost, and the relay host to the outside world by a uucp connection. Mail is distributed using the /etc/mail/aliases files. No naming service is required.

Figure 2-2  Local mail configuration with a uucp connection.

To set up this kind of mail configuration (assuming that the mail clients mount their mail files from /var/mail on the mailhost), you need the following:

•  The main.cf file on the mailhost. You must edit the file to select a major relay mailer.

•  The default subsidiary.cf file on each mail client system (no editing required).

•  A server designated as the mailhost. (Add mailhost to the /etc/hosts file on the mailhost; add the mailhost IP address line to the /etc/hosts file of all mail clients.)

•  Matching /etc/mail/aliases files on any system that has a local mailbox.

•  Entries in each mail client's /etc/vfstab file to mount the /var/mail directory when mailboxes are located on the mail server.

See Chapter 3 for detailed information on how to set up mail services.