Two Domains and a Gateway

The mail configuration shown in Figure 2-3 has two domains and a mail gateway. In this configuration, the mail server, the mail host, and the mail gateway (or gateways) for each domain are likely to be different systems. To make the process of administering and distributing mail easier, a name service is used.

Figure 2-3 Two Domains and a Gateway

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:

• Complex gateway systems requiring a customized sendmail.cf file with special rules added

• The main.cf file on the mail gateway (no editing required if you use MX records)

• 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+)

• An alias entry for each user, to point to where the mail is stored, in mail_aliases.org_dir for NIS+ or the aliases map for NIS

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

• 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