To build a sendmail.cf file customized for your site, you have to write a sendmail.m4 file, and process it with m4. In /usr/local/lib/mail/CF, you find a sample file called sample.m4. Copy it to yourhostname.m4, and edit it to reflect the situation of your site.
The sample file is set up for a UUCP-only site that has domainized headers and talks to a smart host. Sites like this only need to edit a few items.
In the current section, I will only give a short overview of the macros you have to change. For a complete description of what they do, please refer to the earlier discussion of the sendmail.m4.
To create the sendmail.cf file, execute the command
This processes the yourhostname.m4 file and creates yourhostname.cf from it.
Next, you should test whether the configuration file you've created does what you expect it to do. This is explained in the following two sections.
Once you're happy with its behavior, copy it into place with the command:
At this point, your sendmail system is ready for action. Put the following line in the appropriate startup file (generally /etc/rc.inet2). You can also execute it by hand to have the process start up now.
# /usr/lib/sendmail -bd -q1h