eMail notification for comment posting

Hi folks,
I have a question regarding eMail notification in WP 1.5.2 that is not running on my site even if I have toggled on the eMail notification feature in the admin panel and specified my eMail address.
I guess that the problem is more to to with my web hoster that has some restriction concerning php mail functions. The “-f <mail@domain.com>” parameter must allways be specified. So i guess that this parameter is not coded in the WP php files.
What file is launching the mail shipment? I can’t find it. Maybe I am blind.