How to Build a New sendmail.cf File shows you how to build the configuration file. Although you can still use older versions of sendmail.cf files, the best practice is to use the new format.
For more details, refer to the following.
/etc/mail/cf/README provides a complete description of the configuration process.
http://www.sendmail.orghttp://www.sendmail.org provides online information about sendmail configuration.
Versions of the Configuration File and sendmail Configuration File, in Chapter 3, Mail Services (Reference), provide some guidance.
Additional and Revised m4 Configuration Macros From Version 8.12 of sendmail is also helpful.