Diakritika v mailform

Dobry den,
mam problem s mail formom. Mam mailform, ktory mi funguje bez vacsich problemov, az na jednu malickost. Ked zakaznik vyplni tento mailform s diakritikou, tak mi na mail pride necitatelny text (diakritiku nahradzuje znakmi). Neviete please, kde moze byt problem?

Pre istotu sem davam aj kod, co mam v php:

<?php
if(!empty($HTTP_POST_VARS['sender_mail']) || !empty($HTTP_POST_VARS['sender_message']) || !empty($HTTP_POST_VARS['sender_subject']) || !empty($HTTP_POST_VARS['sender_name']))
{
$to = "mail@mail.cz";
$subject = stripslashes($HTTP_POST_VARS['sender_subject']);
$body = stripslashes($HTTP_POST_VARS['sender_message']);
$body .= " --------------------------- ";
$body .= "Mail byl zaslán od: " . $HTTP_POST_VARS['sender_name'] . " <" . $HTTP_POST_VARS['sender_mail'] . "> ";
$header = "Od: " . $HTTP_POST_VARS['sender_name'] . " <" . $HTTP_POST_VARS['sender_mail'] . "> ";
$header .= "Reply-To: " . $HTTP_POST_VARS['sender_name'] . " <" . $HTTP_POST_VARS['sender_mail'] . "> ";
$header .= "X-Mailer: PHP/" . phpversion() . " ";
$header .= "X-Priority: 1";
if(@mail($to, $subject, $body, $header))
{
echo "output=sent";
} else {
echo "output=error";
}
} else {
echo "output=error";
}
?>

moc dakujem, ale mam taky maly problem...php moc neovladam...najde sa tu nejaka dobra dusa, ktora by mi tam pomohla vlozit do toho kodu tu diakritiku?

Predom moc dakujem

mam to vyriesene...na koniec som bol nuteny pochopit php kod na rychlo ....nieje to az tak zlozite, ako som myslel :-)