sendmail.cf

I have a script which sends out email. I set up Error-to: to forward any
errors to the sender through the script. Unfortunately it works when the
domain is invalid but not when the user does not exist on a valid
domain. It returns email to the user nobody.

I have been searching for a solution. I am looking at the "Postfix to
Sendmail compatibility interface" and it discribes the -f option and
that it needs a config file named sendmail.cf in /usr/local/etc/postfix.
Unfortunately I find no mention on what should be in this file.

The system has no user accounts. If any simple solutions exists I would
apreciate the help.

Chris