open MAIL, "|/usr/sbin/sendmail -t -n" or die "mail file error\n";
print MAIL "Reply-to: hogehoge\n";
print MAIL "From: hoge1\@server.com\n";
print MAIL "To: hoge2\@server.com\n";
print MAIL "Subject: TestMail\n\n";
print MAIL "-------------------------------\n\n";
print MAIL "Mail test6 document\n\n";
print MAIL "-------------------------------\n\n";
close MAIL;
で動作しています。