I'd really recommend not doing that either. For one, the syntax for that call looks like:

        $message = "From: blah\nTo: blah\nSubject: blah\n\nmessage\n";
        open (SENDMAIL,"|sendmail -i);
        print SENDMAIL $message;
        close(SENDMAIL);
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Updated:
(Yes, I know it could be done with multiple print's, but I hate dribbling information through a pipe ...)

Which is a bigger rewrite than moving to Net::SMTP:

        use Net::SMTP;

        $smtp = Net::SMTP->new('mailhost');

        $smtp->mail($ENV{USER});       # print MAIL "MAIL FROM ..."
        $smtp->to('postmaster');       # print MAIL "RCPT TO ..."

        $smtp->data();                 # print MAIL "DATA\n";
        $smtp->datasend("line 1\n");   # print MAIL ...
        $smtp->datasend("line 2\n");   # print MAIL ...
        $smtp->datasend("line 3\n");   # print MAIL ...
        $smtp->dataend();

        $smtp->quit;
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Updated: (duh ... typing "first" w/o a "second")
Second, invoking a whole 'nother app (sendmail) when you've already got perl running is just a bunch more overhead on your server. You then also have any security holes in 'sendmail -i' to remember to look for.