.CF File Extension
File TypeSendmail Configuration File
Preference file used to configure the Unix sendmail program; defines the SMTP server, mail relay hosts, and hundreds of other settings; saved in a text format and is compiled by the Unix M4 macro processor each time sendmail is run.
The sendmail configuration file is named "sendmail.cf" and is stored in the following location: /etc/mail/sendmail.cf
NOTE: CF files should not be confused with ColdFusion Markup files, which have a .CFM extension.