sendmail

Sendmail is popular email server used in linux, unix and FreeBSD servers.

sendmail configuration file

You can define most of sendmail's configuration parameters in the /etc/mail/sendmail.mc file, which is then used by the m4 macros to create the /etc/mail/sendmail.cf file.

Configuration of the sendmail.mc file is much simpler than configuration of sendmail.cf, but it is still often viewed as an intimidating task with its series of structured directive statements that get the job done. Fortunately, in most cases you won't have to edit this file very often.