<?php
if($_FILES['fileFF']['size'] > 0) {

  $output = '<h1>Спасибо! Ваш файл получен.</h1>';

  $to = "хуи@мыло.ру"; // адрес почты получателя

  $anon    = htmlspecialchars ($_POST['anon']);
  $from    = htmlspecialchars ($_POST['from']);
  $subject = htmlspecialchars ($_POST['subject']);
  $message = htmlspecialchars ($_POST['message']);

  $attachment = chunk_split(base64_encode(file_get_contents($_FILES['fileFF']['tmp_name'])));
  $filename = $_FILES['fileFF']['name'];
  $filetype = $_FILES['fileFF']['type'];

  $boundary = md5(date('r', time())); // рандомное число

  $headers = "From: $anon <" . $from . ">\r\n"; // см. наиболее часто используемые заголовки
  $headers .= "Reply-To: <" . $from . ">\r\n";
  $headers .= "MIME-Version: 1.0\r\n";
  $headers .= "Content-Type: multipart/mixed; boundary=\"_1_$boundary\"";

  $message="
--_1_$boundary
Content-Type: multipart/alternative; boundary=\"_2_$boundary\"

--_2_$boundary
Content-Type: text/plain; charset=\"utf-8\"
Content-Transfer-Encoding: 7bit

$message

--_2_$boundary--
--_1_$boundary
Content-Type: \"$filetype\"; name=\"$filename\"
Content-Transfer-Encoding: base64
Content-Disposition: attachment // содержимое является вложенным

$attachment
--_1_$boundary--";

  mail($to, $subject, $message, $headers);

}
?>

<!DOCTYPE HTML>
<html>

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Свзяь с администрацией</title>
</head>

<body>
<style>
html, body {
    margin: 0;
    padding: 0;
    font: 14px/1.6 Georgia, Palatino, Palatino Linotype, Times, Times New Roman, serif;
    color: #333;
    background: #eee;
}

.form {
    padding: 10px;
    background: #FCFCFC;
    width: 500px;
    margin: 0 auto;
}

textarea {
    width: 494px;
}

.file {
    width: 100px;
    height: 40px;
}
</style>

<?php echo $output; ?>

<div class="form">
    <form enctype="multipart/form-data" method="post">
        <input type="text" name="subject" placeholder="Subject Message"><br />
        <input type="text" name="anon" placeholder="Your Name"><br />
        <input type="text" name="from" placeholder="Your E-Mail"><br />
        <textarea name="message" placeholder="Your Text"></textarea><br />
        <input type="file" class="file" name="fileFF"><br />
        <input type="submit" value="Отправить">
    </form>
</div>

</body>
</html>