Sendmail.cf question: Ignoring smart relay for local mail

[Joel Hammer]

I have a firewall box which runs sendmail, which routes
all mail to my comcast mailserver (Otherwise, my mail
bounces). This works fine except when I want to send
mail locally from the firewall box to other boxes on
the network.

I know there are M4 macros for doing this, but I am
determined not to get involved with that, since I have
a perfectly good sendmail.cf file and have no desire to
tinker more than necessary.

I can brute force this by running sendmail manually with
the -C option to point to another sendmail.cf; but, I
would like to know a way to edit sendmail.cf to handle
this automatically.

Thanks,

Joel