if (-e "/usr/bin/sendmail") {
    $sendmail = "/usr/bin/sendmail";
}#if
if (-e "/usr/sbin/sendmail") {
    $sendmail = "/usr/sbin/sendmail";
}#if
if (-e "/usr/lib/sendmail") {
    $sendmail = "/usr/lib/sendmail";
}#if
if (-e "/var/qmail/bin/qmail-inject") {
    $sendmail = "/var/qmail/bin/qmail-inject";
}#if