[exim] Webserver relay only exim config

Does anyone have a config that is suitable for use on a webserver, where the
webserver will accept messages only on localhost 25 and forward all mail to
a smarthost, and it will accept mail with the sendmail -oi -t switches
common to CGI scripts and write the Sender headers, etc, with whatever is
set in the From: field?

Thanks,

Nathan.