[mail function] ; For Win32 only. SMTP = localhost smtp_port = 25 ; For Win32 only. sendmail_from = me@mydomain.prg ; For Unix only. You may supply arguments as well (default: "sendmail -t -i"). ;sendmail_path = ; Force the addition of the specified parameters to be passed as extra parameters...

A possible way of providing per-site PHP configuration on IIS 7.0 is described here: http://learn.iis.net/page.aspx/208/#Per-site .