Imposta il charset corretto nella mail.

Da php.net fra i commenti alla funzione mail.
Zane @ MLI08-Sep-2010 10:17

Italian users cursing against "È" and other uppercase-accented-vowels ("vocali maiuscole accentate"") in subjects! While the lowercase ones ("è", "é" and so on) work as expected, qmail doesn't handle the uppercase ones.

To fix it, the only way I found was this:

<?php

function mail_utf8($to, $subject = '(No subject)', $message = '', $header = '') {
$header_ = 'MIME-Version: 1.0' . "\r\n" . 'Content-type: text/plain; charset=UTF-8' . "\r\n";
mail($to, '=?UTF-8?B?'.base64_encode($subject).'?=', $message, $header_ . $header);
}

?>

It should apply to other languages too.