自作PHPメールフォームでメールが受信できません。

syapapaさん

自作PHPメールフォームでメールが受信できません。

自作で作成したＰＨＰメールが受信できません。
入力した人に返送するConfirmationメールは正常に送信できているのに、アドミの方にはメールが送信されません？受信できない？状況です。いろいろと試しているものの解決しません、基本的な間違いをしてるかも知れませんが、自己解決ができないのでご教授下さい。

Current PHP version: 4.3.11
サーバー：Yahoo(米国）レンタルサーバー

====CODE====
mb_language('ja');
mb_internal_encoding("UTF-8");

//Create Short Variable Names
$str_sub = $_POST['sub'];
$str_cate = $_POST['cate'];
$str_name = $_POST['name'];
$str_phone = $_POST['phone'];
$str_email = html_entity_decode ($_POST['email'], ENT_COMPAT, 'UTF-8');
$str_comme = $_POST['comme'];
$header= "Category: " .$str_cate . " Subjefct:" .$str_sub;

//Email Address for Administrator
$toaddress = "admin@gmail.com";
$mailcontent .= "Subject: " .$str_sub ."\n";
$mailcontent .= "Comment: " .$str_comme ."\n\n";
$mailcontent .= "-----\n";
$mailcontent .= "Name: " .$str_name ."\n";
$mailcontent .= "Phone: ".$str_phone ."\n";
$mailcontent .= "E-mail: " .$str_email ."\n\n";
$mailcontent .= "-----\n";

//Auto Message for a Customer
$header2 = "Test has received your mail";
$from = "noreply@test.com";
$toaddress2 = $str_email;
$body = "Hello " .$str_name .",\n\n";
$body .= "Thank you! Your inquiry has been submitted to test. We will be in contact with you via E-mail within a couple business days. \n\nBest Regards, \n\nTest \n\n";
$body .= "----- Questions/Comments ----- \n";
$body .= $str_comme ."\n\n";
$body .= "----- Your information ----- \n";
$body .= "Name: " .$str_name ."\n";
$body .= "Phone: " .$str_phone ."\n";
$body .= "Email: " .$str_email ."\n";
$body .= "-----";

//Send data to admin
mb_send_mail($toaddress2,$header,$mailcontent,"From:$email");
//Send date to customer
mb_send_mail($toaddress,$header2,$body,"From:$from");
====/CODE====

まだまだ未熟者で原因がまったくわかりません、どうぞお力添えをお願いいたします。