You can configure your mail system in several modes. The most basic mode is a local network environment, where two or more workstations are connected to one mail host. This local network environment is not connected to the outside world. You can configure mail for a more complex network environment, such as a two-domain configuration attached to a mail gateway. You can decide on the type of mail configuration you want to set up based upon your requirements.
Regardless of the mode in which you configure your mailing service, you need the following elements:
A mailbox to store or spool mail for each user.
A sendmail.cf configuration on each system running sendmail.
Alias files with an alias for each user to point to the ...