On my machine, these are the relevant lines in sendmail.mc:
Code:
dnl #
dnl # Uncomment and edit the following line if your outgoing mail needs to
dnl # be sent out through an external mail server:
dnl #
define(`SMART_HOST',`my.isp.net')dnl
After editing sendmail.mc, run make in the /etc/mail directory and then restart your mail server to make the changes take effect.