The most common mail configuration in a small network is shown in Figure 34-2. One system is the mail server, the mail host, and the mail gateway to the outside world. Mail is distributed using the /etc/mail/aliases files. No name service is required.
To set up this kind of a mail configuration, assuming that the mail clients mount their mail files from /var/mail on the mail host, you need:
The main.cf file on the mail gateway (no editing required if MX records are used)
The default /etc/mail/sendmail.cf file on each mail client system (no editing required)
A server designated as the mail host (add mailhost.domainname to the /etc/hosts file on the mail host; if you are not running NIS or NIS+, add the mail host 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 (unless you are running NIS or NIS+)
Entries in each mail client's /etc/vfstab file or /etc/auto_direct (if autofs is used) to mount the /var/mail directory when mailboxes are located on the mail host
Enough space in /var/mail on the mail server to hold the client mailboxes