A Super Search on Sendmail would have given you lots of relevant nodes. So here just a few hints:
The path to sendmail varies from nix-box to nix-box, your apache server (apache is just the webserving software, not an OS) might have it in

my $mailprog = "/usr/lib/sendmail"; or
my $mailprog = "/usr/bin/sendmail";
[download]

or somewhere else entirely. Your friendly sysadmin will be able to tell you.

There is a sendmail for Win, but that is not necessarily installed on the box the IIS is running on. To be on the safe side you could use Net::SMTP, which runs on both platforms, but also is not guaranteed to be installed.

neophyte Niederrhein.pm