Можно изменить функцию fileAttachment, файл на русском будет перекодирован в латиницу.
public static function fileAttachment($input = 'fileUpload', $return_content = true)
{
$file_attachment = null;
if (isset($_FILES[$input]['name']) && !empty($_FILES[$input]['name']) && !empty($_FILES[$input]['tmp_name']))
{
$f = $_FILES[$input]['name'];
$f = (string) $f;
$f = strip_tags($f);
$f = str_replace(array("\n", "\r"), " ", $f);
$f = preg_replace("/\s+/", ' ', $f);
$f = trim($f);
$f = Tools::strtolower($f);
$f = strtr($f, array('а'=>'a','б'=>'b','в'=>'v','г'=>'g','д'=>'d','е'=>'e','ё'=>'e','ж'=>'j','з'=>'z','и'=>'i','й'=>'y','к'=>'k','л'=>'l','м'=>'m','н'=>'n','о'=>'o','п'=>'p','р'=>'r','с'=>'s','т'=>'t','у'=>'u','ф'=>'f','х'=>'h','ц'=>'c','ч'=>'ch','ш'=>'sh','щ'=>'shch','ы'=>'y','э'=>'e','ю'=>'yu','я'=>'ya','ъ'=>'','ь'=>''));
$f = preg_replace("/[^0-9a-z-_. ]/i", "", $f); // очищаем строку от недопустимых символов, только цифры + буквы + точка
$f = str_replace(" ", "-", $f);
$file_attachment['rename'] = uniqid(). (substr($f, -5));
if ($return_content)
{
$file_attachment['content'] = file_get_contents($_FILES[$input]['tmp_name']);
}
$file_attachment['tmp_name'] = $_FILES[$input]['tmp_name'];
$file_attachment['name'] = $f;
$file_attachment['mime'] = $_FILES[$input]['type'];
$file_attachment['error'] = $_FILES[$input]['error'];
$file_attachment['size'] = $_FILES[$input]['size'];
}
return $file_attachment;
}