The most common mail configuration in a small network is shown in Figure 25-2. One system includes the mail server, the mail host, and the mail gateway to the outside world. Mail is distributed by using the /etc/mail/aliases files on the mail gateway. No name service is required.
In this configuration, you can assume that the mail clients mount their mail files from /var/mail on the mail host. To set up this kind of mail configuration, you need the following.
The main.cf file on the mail gateway (no editing is required if Mail Exchanger [MX] records are used).
The default /etc/mail/sendmail.cf file on each mail client system (no editing is required).
A server that is designated as the mail host. You can make this designation by adding mailhost.domain_name to the /etc/hosts file on the mail host. Then, if you are not running NIS or NIS+, add the IP address line for the mail host to the /etc/hosts file of every mail client.
Matching /etc/mail/aliases files on any system that has a local mailbox (unless you are running NIS or NIS+).
Enough space in /var/mail on the mail server to hold the client mailboxes.
For task information on setting up your mail service, refer to "Setting Up Mail Services (Tasks)". If you are looking for a particular procedure that is related to setting up your mail service, refer to "Setting Up Mail Services (Task Map)".